We've recently had some discussions on ~transport about the negative impacts of SUVs (among other things) on pedestrian fatalities. In short: statistically, large and heavy cars universally kill...
We've recently had some discussions on ~transport about the negative impacts of SUVs (among other things) on pedestrian fatalities. In short: statistically, large and heavy cars universally kill more pedestrians than small, light ones. But there's more to the story. Evidently, there are multiple factors at play! Just as much or more than weight, higher vehicle speed leads to more pedestrian fatalities:
Tennessee's decade-long surge in pedestrian deaths has less to do with the size of the cars that strike walkers than the speed of roads on which they were struck, according to a new study finds that could have big implications for policymakers in other car-dependent states.
In a new paper published in Transportation Research Record, analysts found that the Volunteer State's 117-percent increase in pedestrian deaths between 2009 and 2019 was tightly correlated with an increasing number of crashes on straight, multi-lane roads with speed limits over 35 miles per hour in urban and suburban areas — or, as they're better known among Vision Zero advocates, arterial "stroads" that combine the features of neighborhood streets with a car-oriented roads to deadly effect.
And contrary to another wildly popular hypothesis, the researchers also found that, at least in Tennessee, the increasing prevalence of big SUVs and pick-up trucks wasn't the factor driving the death surge — though that doesn't mean they don't need regulation, particularly in places where stroads have been tamed.
Researchers are clear that larger cars are more dangerous. At a given speed, the force transmitted onto a pedestrian's vulnerable skeleton is inherently higher during a collision caused by a heavy vehicle than a light one. And the larger the vehicle, the worse the visibility for Vulnerable Road Users (VRUs), including pedestrians and cyclists, and especially children. In other words: big cars are bad for society.
However, above a certain speed, it doesn't matter how big the car is: pedestrians are going to die when hit. This includes speeds drivers frequently take on "arterial" roads, or larger collector roads that typically prioritize automobile throughput at the expense of pedestrian comfort. At speeds around 50mph, pedestrians have only a 10% chance of surviving being hit by a car. Hussain et al. 2019 conduct a meta-analysis of 20 traffic studies and determine that:
The risk of a fatality reaches 5% at an estimated impact speed of 30 km/h [19 mph], 10% at 37 km/h [23 mph], 50% at 59 km/h [37 mph], 75% at 69 km/h [43 mph] and 90% at 80 km/h [50 mph].
The study proposes that "high pedestrian active areas" should impose a speed limit not exceeding ~25 mph. But safety advocates want to ensure that this doesn't just affect local neighborhood streets, but also any higher-traffic arterial that might see pedestrians. The risk of death skyrockets between 20 and 40 mph, with the higher end of the range demonstrating a 50% fatality rate.
In the United States, it's common for arterial speed limits to be 45 mph or higher. Additionally, drivers routinely break speed limits, demonstrating a particular likelihood to exceed posted arterial speed limits in the minutes after exiting the freeway. This is commonly understood: whatever the speed limit, some number of people test it by 5–10 mph or sometimes more. It is therefore prudent to reduce speed limits beyond what they currently are, including on arterial roads. The only roadway which has no pedestrian interaction is a grade-separated or fully enclosed highway. On any other road, including arterials, it is essential to prioritize human life over traffic throughput, especially as pedestrian deaths are on the rise.
Going to have a slightly pedantic statement to disagree here. There isn't more to the story or multiple factors at play. Larger, heavier vehicles are deadlier. Full stop. Higher speeds are...
But there's more to the story. Evidently, there are multiple factors at play!
Going to have a slightly pedantic statement to disagree here.
There isn't more to the story or multiple factors at play. Larger, heavier vehicles are deadlier. Full stop.
Higher speeds are deadlier as well. But the two are independent of one another; if nothing else changed except the replacement of every SUV/CUV with a Camry, the number of lives lost would go down.
If nothing else changed except lower speeds, the number of lives lost would go down.
The factors involved aren't SUVs and speed. It's two independent factors that are worse when combined. SUVs have no purpose to the average driver that can't be solved by a smaller/lighter vehicle.
I've said it before, I'll say it again. Unless someone has the regular need to tow something of considerable weight while also requiring the accommodations of three rows of seating simultaneously, then they don't need an SUV and should be in a car or a van.
You have stated that there are multiple factors at play: one being weight, one being speed. Indeed, they independently contribute to pedestrian fatalities, but also amplify each other. Both of...
You have stated that there are multiple factors at play: one being weight, one being speed. Indeed, they independently contribute to pedestrian fatalities, but also amplify each other. Both of these metrics are important, which is what the purpose of this thread is.
I agree that there is no need for the majority of people to own a particularly large vehicle, including an SUV. Most states have a weight-based registration fee for automobiles, but it's a paltry amount. People really need to be charged thousands of dollars for registering an SUV, with tax credits or some other exception for people who can demonstrate a real need for the vehicles. Their danger to society is just too great.
My opinion is that the regulatory incentives to build larger SUVs need to be reversed. In the US at least, automakers are indirectly incentivized to produce larger SUVs due to the structure of...
My opinion is that the regulatory incentives to build larger SUVs need to be reversed. In the US at least, automakers are indirectly incentivized to produce larger SUVs due to the structure of fuel economy regulations.
The CAFE standards established in 2012 introduced a size-based efficiency curve. This meant that larger vehicles, like SUVs and light pickup trucks, had fuel efficiency targets that got relatively less stringent the larger the vehicle got.
Consequently, when faced with regulations meant to improve the fuel efficiency of their existing vehicles, automakers chose to instead increase the size of SUVs and trucks to fit a more lenient part of the curve.
I have to respectfully disagree with that idea. That seems like a way of saying "the wealthy can have it no matter what, but the poor can only have it if they need it." I'm not saying that SUV's...
People really need to be charged thousands of dollars for registering an SUV, with tax credits or some other exception for people who can demonstrate a real need for the vehicles.
I have to respectfully disagree with that idea. That seems like a way of saying "the wealthy can have it no matter what, but the poor can only have it if they need it." I'm not saying that SUV's should or shouldn't be regulated, as I don't really have an opinion on that, but wealth should not play any part in the regulation.
Ya know, completely off topic, but I find it burdensome to have to consider socioeconomic implications every time literally anything needs to be implemented. Hear me out before you consider me an...
Ya know, completely off topic, but I find it burdensome to have to consider socioeconomic implications every time literally anything needs to be implemented. Hear me out before you consider me an uncaring asshole.
There's lots of issues where ultimately the solution, the problem, or anything in between is that "things get expensive" or that the distribution of prices changes, or what have you. Energy crisis in Europe? Well, the poorest won't be able to compete on price, so won't be able to heat their homes. Make trucks more expensive to dissuade people? Now the poorest won't be able to buy SUVs. I won't bore you with more details. Anytime one of these issues comes up, there's socioeconomic considerations inserted into the discussion, even though in principle the topics have nothing to do with socioeconomics. This makes a lot of these discussions endlessly tiring. And I'm not a fan. Ultimately, socioeconomic issues should be solved independently: Tax rich people more, give nonmonetary and monetary assistance to poor people. Once that's in place to an acceptable degree, making SUVs more expensive, or taxing CO2 emissions, or what have you, becomes much simpler, as the social issue isn't overshadowing whatever you're trying to fix. Giving poor people an SUV tax break, or an energy tax break, or otherwise omitting them from these financial tools we're using to shape collective behavior is (1) socioeconomic policy in varying degrees of disguise (2) weakens the policy wrt. its intended goals and (3) makes the implementation of that policy much more complicated. (e.g. in this case by bloating the number of tax breaks available - btw, this complexity benefits the rich)
Make social policy stay in its lane, and make it sufficiently strong that you don't have to worry about it every damn time you touch literally anything.
I'm well aware that as long as such a sound baseline of socioeconomic policy isn't in place, we have to consider side effects of policy, but man things could be so much simpler.
I think you've slammed the nail on the head with what I've failed to articulate lately. "SUVs are more dangerous and should be taxed by weight to discourage the purchase of them." "But then poor...
I think you've slammed the nail on the head with what I've failed to articulate lately. "SUVs are more dangerous and should be taxed by weight to discourage the purchase of them." "But then poor people couldn't buy SUVs!"
As if we were arguing over the 'right to run over pedestrians' as opposed to the right to scoot about town in three tons powered by explosions while staring at your phone. Yeah, poor people can't afford a lot of things, still doesn't make SUVs a necessity. Not like the truly economically disadvantaged are the ones buying them as opposed to getting run over by them while walking to the bus.
Your sentiment is noble, and I agree that it would be nice to find a solution that is not based on income. What is your proposal to equitably decrease SUV use across the board?
Your sentiment is noble, and I agree that it would be nice to find a solution that is not based on income. What is your proposal to equitably decrease SUV use across the board?
I feel like a license class for an SUV would be appropriate, similar to class A and B licenses that require extra learning and proof of ability to drive the larger vehicles. There are different...
I feel like a license class for an SUV would be appropriate, similar to class A and B licenses that require extra learning and proof of ability to drive the larger vehicles. There are different rules that should be used when driving an SUV compared to a sedan and these should definitely be part of it. Drivers should be educated on, and be able to demonstrate abilities related to, larger gaps between vehicles at speed, different emergency maneuvers to prevent roll overs, dealing with larger blind spots on the road and in parking lots, and towing/cargo management. I think just adding a required license would cut down on the number of SUV drivers and improve the overall capabilities of the licensed drivers.
I agree that more licensing would be a good solution to cut down on SUV use. (I would still favor exaggerating our weight-based fees, because those remaining drivers are still contributing...
I agree that more licensing would be a good solution to cut down on SUV use. (I would still favor exaggerating our weight-based fees, because those remaining drivers are still contributing negatively to the safety environment, but maybe it could be a bit lower to account for the decrease in SUV use induced by a license.)
Do you think that more licensing could work politically? Should it apply retroactively, or just moving forward?
If by "politically" you mean acceptance by society, I would say that there would be uproar over it but it has been done before (since we do have licensing requirements in every state). I...
If by "politically" you mean acceptance by society, I would say that there would be uproar over it but it has been done before (since we do have licensing requirements in every state). I definitely think it would be a hard sell to any politician because of the impact it could have on their political careers and that it would be the next political hot topic because of how many people it would affect. If it actually made it to a vote then the opinions of the citizens should certainly weigh heavily on the vote.
I don't personally like the idea of retroactively applying laws, especially when it is something that is so heavily tied to a household's finances. I would have to say it should only apply moving forward. I know that means the problems created by SUV's would decline more slowly, but there has to be a balance between creating a safer environment and people being able to maintain their financial livelihood.
I’ll come back and say we can address that by increasing the tax burden on luxury. So a tax based on weight, and a second tax based on msrp, where the tax increases exponentially as price...
I’ll come back and say we can address that by increasing the tax burden on luxury.
So a tax based on weight, and a second tax based on msrp, where the tax increases exponentially as price increases from 33rd percentile.
The obvious follow-up question to the existence of this lethal velocity is "What is the lethal velocity of SUVs vs that of smaller cars?" If smaller cars are safer for pedestrians, isn't it a...
The obvious follow-up question to the existence of this lethal velocity is "What is the lethal velocity of SUVs vs that of smaller cars?" If smaller cars are safer for pedestrians, isn't it a guarantee that SUVs simply reach that lethal speed sooner? I mean, it sounds to me like the two discussions (car size vs car speed) are more or less orthogonal in the sense that both increase lethality, but there's no unexpected interactions. That this lethal velocity exists, at which point the vehicle type doesn't make a difference, doesn't mean that vehicle type is unimportant.
Or in other, slightly cynical words: Given a certain tolerance of lethality (including zero), the speed of traffic could be higher if everyone just drove sensibly-sized cars.
I had the same question. The 2019 study I linked appears to analyze all motor vehicles, including sedans, SUVs, vans, light trucks, and probably heavy trucks. The figures shown would therefore...
I had the same question. The 2019 study I linked appears to analyze all motor vehicles, including sedans, SUVs, vans, light trucks, and probably heavy trucks. The figures shown would therefore appear to be averages based on 2019 usage data for each of these vehicle classes. Maybe you could do some speculative weighting math to figure out how the proportion of ownership of vehicles of a particular weight class affects those averages.
Passenger cars and light trucks (vans, pickups, and sport utility vehicles) accounted for 46.1% and 39.1%, respectively, of the 4875 deaths, with the remainder split among motorcycles, buses, and heavy trucks. Compared with cars, the [relative risks] of killing a pedestrian per vehicle mile was 7.97 (95% CI 6.33 to 10.04) for buses; 1.93 (95% CI 1.30 to 2.86) for motorcycles; 1.45 (95% CI 1.37 to 1.55) for light trucks, and 0.96 (95% CI 0.79 to 1.18) for heavy trucks. Compared with cars, buses were 11.85 times (95% CI 6.07 to 23.12) and motorcycles were 3.77 times (95% CI 1.40 to 10.20) more likely per mile to kill children 0–14 years old. Buses were 16.70 times (95% CI 7.30 to 38.19) more likely to kill adults age 85 or older than were cars.
The relative risk factor is compared to a baseline of 1, so in this case the risk of fatality per vehicle mile traveled (VMT) is apparently 1.45 for light trucks for the general population. But that is not strictly the metric we're looking for, because it evaluates overall danger based on overall usage (which could be influenced by various other behaviors independently resulting from differences in absolute distance traveled) rather than danger of one type of vehicle vs. another at a particular speed. So I don't think you can use the relative risk of fatality for a particular vehicle class shown in this study to directly calculate optimal speed limits for each vehicle class.
As a rough approximation that would probably infuriate real statisticians, maybe you could use that relative risk of 1.45 to enforce a 45% lower speed limit everywhere. Or maybe you could weight it to the portion of vehicles owned which are SUVs and apply that resultant speed limit (so, idk, 20% lower, I'm not doing that math) everywhere. But that's probably an excessive reaction considering buses have an RR of 7.97. (What are you going to do there? Enforce a 0 mph speed limit?)
SUVs remain disproportionately likely to injure and kill pedestrians compared with cars, but these differences emerged primarily at crashes of intermediate speed. Crashes at low speeds and high speeds tend to produce similar injury outcomes independent of striking vehicle type (mild and fatal, respectively). The data suggest that the elevated danger to pedestrians from SUVs in these crashes may be largely related to injuries caused by impacts with the vehicles’ leading edge: the bumper, grille, and headlights.
...but I can't access the article to read the actual speed statistics.
Kröyer 2014 suggests that SUVs are also more dangerous at a given speed (I assume), and offers several remarks about other factors that influence the dangerousness of SUVs beyond weight alone:
The literature review shows that the risk of severe injuries is higher for Sport Utility Vehicles (SUVs), Light Truck Vehicles (LTVs) and trucks compared to passenger vehicles [4], [17], [18], [19]. The fatality risk is also higher for LTVs and SUVs compared to passenger vehicles [4], [5], [6], [18], [20]. Three design factors where the SUV and LTV differ from the passenger vehicle affect the mechanisms of the collision: they are stiffer, have higher bumpers and are heavier [5]. Other studies have pointed out that it is not the weight, but rather the front structure that affects the injury severity [21]. Since the weight of any vehicle is so much greater than the weight of a pedestrian, the resulting acceleration for the human body in an impact can hardly make a significant difference.
The article doesn't explicitly analyze what a "safe speed" is for SUVs vs. sedans, but you can roughly and unscientifically extrapolate that what constitutes a "fatal injury" for an SUV collision with a pedestrian might be approximately equivalent to a "severe [but non-fatal] injury" for a sedan collision. This particular study states that a fatal pedestrian injury occurs when the offending vehicle has a mean speed of 48.9 km/h (30.4 mph) and a severe (but non-fatal) injury occurs when the offending vehicle has a mean speed of 40.5 km/h (25.2 mph).
So you might be able to say, as a quick approximation (because I can't find a study that answers this specific question with specific numbers for different vehicle classes), that driving an SUV is like driving a sedan 5 mph faster; or that an SUV driving at 25 mph would kill a pedestrian whereas a sedan would only severely injure them. But again, that is not explicitly what this dataset says, that is just a rule-of-thumb extrapolation I've made for the purposes of this discussion.
In any case, the fact remains the same: high speeds kill. Because some vehicles on the road are always going to be fairly large (whether SUVs, vans, or delivery trucks), it is worth considering this factor when choosing which speed limit to enforce on a particular street.
I mean, some cars have good excuses for being dangerous: I reckon busses are so dangerous because they're by definition close to pedestrians, and are also by definition heavy. That's a target rich...
I mean, some cars have good excuses for being dangerous: I reckon busses are so dangerous because they're by definition close to pedestrians, and are also by definition heavy. That's a target rich environment. (If I'm right about the reasons there, I expect busses to have mostly excess slow-speed collisions compared to trucks.) Heavier trucks have the "excuse" that they are actually using all of that extra weight to lug around heavy goods. SUVs have none of these excuses. I could see, for example, a rule where vehicles in a certain weight class have to stay X below the speed limit. >2t? 5 under you drive. >5t? 10 under. Well, I could see this from a risk management perspective. The traffic flow implications are atrocious. Alternatively, a pressing need to operate such a heavy vehicle could somehow be required implicitly or explicitly. Special license required for heavy vehicles that's extra work to get? Suddenly only professional drivers with heavy goods will only find heavy vehicles appealing, as opposed to small people with big egos. Whatever cutoff you choose there for what is a heavy vehicle is then the standard for the purposes of speed limits. If 2t vehicles require special licenses, then you design roads s.t. 1.99t vehicles are slow enough not to kill pedestrians too often.
You can use momentum (mass x velocity) or kinetic energy (0.5 x mass x velocity^2) to compare the combined mass and velocity. It's more a simple physics modeling problem than a statistical one. At...
You can use momentum (mass x velocity) or kinetic energy (0.5 x mass x velocity^2) to compare the combined mass and velocity. It's more a simple physics modeling problem than a statistical one. At best, given the same velocities, a more massive object scales the output figure linearly. And when we're talking 5000lb SUVs vs 3500lb hatchbacks, that's very significant.
I don't think a linear relationship holds, especially since not all velocity is expended during a collision with a pedestrian. A very light vehicle that actually slows down due to the collision,...
I don't think a linear relationship holds, especially since not all velocity is expended during a collision with a pedestrian. A very light vehicle that actually slows down due to the collision, sure, more or less linear there. But once the vehicle is so heavy that it actually doesn't appreciably slow down due to the collision, you might as well consider the mass infinite and be more or less correct. At which point all the soft factors mentioned by scroll_lock come into play. So I don't think it's weight per se that kills, it's just that it makes all the soft factors worse. But if you doubled brakes, engine, and weight of a given car without changing the dimensions or anything else, I don't actually think it'd make a noticeable difference. The difference would be that the car slows down from 50 to either 48 or 49 mph due to the collision, and that's it.
Yes, though as some of the research notes, the physical design of an automobile (especially its grill, which is what comes into contact with pedestrian victims) has an effect on pedestrian...
Yes, though as some of the research notes, the physical design of an automobile (especially its grill, which is what comes into contact with pedestrian victims) has an effect on pedestrian fatality rates. SUVs have different characteristics than sedans beyond weight. For example, whether they are likely to end up on the dashboard, flung to the side, or crushed below the wheels. Additionally, SUVs have lower visibility which affects the frequency of collisions with pedestrians in the first place. Factors like these influence the overall "danger" of a particular vehicle class, so it's still important to use real-world data where available.
I think your model can give us a pretty good sense of how driving a battery-electric vehicle (heavy) rather than an ICE vehicle of the same class might affect safety, though.
Yes. I've seen that concern a lot in the past, and it makes a lot of sense. If you stand next to a Camry or Fit, the car would hit you in the legs and you'd roll across the hood, which mitigates...
Yes. I've seen that concern a lot in the past, and it makes a lot of sense. If you stand next to a Camry or Fit, the car would hit you in the legs and you'd roll across the hood, which mitigates some of the force applied and keeps you out from under the car.
The typical SUV and contemporary truck strikes most people in the upper chest or head, and drives over them. So the way the kinetic energy is delivered is also worse than on a small vehicle...but either way, an SUV has a much higher KE at the same velocity, and even soemewhat higher velocities. Both are definitely an issue.
Having briefly rented a Yukon (because they had no minivan offerings for a road trip), it's also shocking how poor the visibility and maneuvering are. You pretty much need to rely on sensors and cameras for merging right or backing up, because there are so few spots that aren't blind it's ridiculous. You also would never see some or under five feet tall standing directly in front of the vehicle, and pedestrians at a crosswalk would easily be difficult in general.
I'm generally in favor of regulating SUVs out of existence and requiring a form of commercial licensing for pickup trucks, with heavy taxation.
I don't have time at the moment to read the article in it's entirety so perhaps you could answer a question: is a reason proposed anywhere for the actual increase? Speed kills, sure, but are cars...
I don't have time at the moment to read the article in it's entirety so perhaps you could answer a question: is a reason proposed anywhere for the actual increase? Speed kills, sure, but are cars driving faster now than 10+ years ago? Are more pedestrians walking on the stroads? Are more stroads being built?
The hypothesis championed in the article and by the report is "the suburbuanization of poverty" which basically means that there is an increased amount of pedestrians on stroads. So it's not that...
The hypothesis championed in the article and by the report is "the suburbuanization of poverty" which basically means that there is an increased amount of pedestrians on stroads.
So it's not that there are more stroads or people are going faster, it's that more people walking along them now means more opportunities for the chance of a pedestrian collision.
That is what the report postulates. Technically, you can extend this concept as it relates to traffic safety to any area where there is a modal and/or demographic shift. Whether or not the change...
That is what the report postulates. Technically, you can extend this concept as it relates to traffic safety to any area where there is a modal and/or demographic shift. Whether or not the change in the last 10 years is linked to poverty specifically (which I would believe, but can't definitively comment on), more people beginning to walk in an area that has traditionally had a lot of cars (and car-centric infrastructure) and few pedestrians means that there will be more pedestrian fatalities from collisions. Likewise, more people beginning to drive in an area that has traditionally had primarily pedestrian traffic can result in more people being injured and killed by motor vehicles.
That's an almost impossibly simplistic observation, and yet city officials do not necessarily incorporate reasonable safety measures along stroads and within neighborhoods that are seeing growth or modal shifts. Philadelphia's Washington Avenue, one of the city's most dangerous stroads, has seen a significant amount of residential development in the last few years. Yet despite all the anticipated foot and bike traffic, the city failed to properly implement a road diet, install protected bike lanes, and otherwise reduce driver speeds; what changes have been made are severely lacking.
As another example, this problem may be more evident in parts of the city's Northern Liberties neighborhood, which is right next to exits from I-95 and I-676, places where drivers are likely to exhibit highway-speed driving along what is technically an urban arterial. Callowhill Street near 2nd Street is nightmarishly wide and drivers routinely demonstrate reckless behavior there; this is despite the street dividing the neighborhood from the dynamic and lively Old City neighborhood. In other words, even though both Northern Liberties and Old City are growing rapidly, the city fails to redevelop around people; instead preferring a status quo which prioritize automobile throughput.
But this isn't a problem unique to Philly. City planners generally have good intentions—they're big on urbanist concepts and want communities to thrive. But through a combination of misinformation, inattention, and pressure from managers, consultants, or political appointees who are either not educated in urban planning or simply represent the interests of automobile users, many municipalities fail to make meaningful safety improvements to their streets. It is therefore important for constituents to be aware of the literal dangers of the status quo and to advocate for safer streets in community meetings and with their elected representatives.
Well, recently there was an accident when woman driving such car went over a kid in the town doing slow speed. Kid didn't survive. Why she ran the kid over? She couldn't see the first 9 meters...
Well, recently there was an accident when woman driving such car went over a kid in the town doing slow speed. Kid didn't survive. Why she ran the kid over? She couldn't see the first 9 meters ahead of her car frm driver's seat! Freaking 9 meters, that's 30 feet! If you can't see this distance in front of your car, something is not right. I'm not saying the car is the problem here. I'm saying that car makers making such cars are the problem. And small person sitting behind the wheel.
There was this image where SUV driver was saying how great the view from he car is sitting high above street level with kids playing in front of the car that were invisble to the driver. This is what just happened here, no more just a comic strip that wants to show the dangers, but reality.
Hi, as a person outside of US what the spees limit in the cities? Where I live recently (few years ago) govt provided new speed limit in city - 50km/hr, 30 mph. Previously it was 70km/hr, 43mph....
Hi, as a person outside of US what the spees limit in the cities? Where I live recently (few years ago) govt provided new speed limit in city - 50km/hr, 30 mph. Previously it was 70km/hr, 43mph. First few months it feels slow, but now it feels perfectly ok.
As another commenter said, it varies greatly state-to-state. Wikipedia has an interesting list of speed limits by jurisdiction. The Department of Transportation has some materials discussing types...
The Department of Transportation has some materials discussing types of places/roads that commonly use different speed limits.
In general—and this is very approximate—most neighborhood streets are superficially intended for fairly slow driving, perhaps around 20–25 mph. They are typically engineered for much faster driving, though—the streets are usually too wide, so drivers don’t obey the limits. (Sometimes, the limits are too high for a residential street, like 30–35 mph.) Very generally, the fastest posted speed limits within an urban area would be on an “arterial” road, probably at most 45–50 mph. School zones usually have very low speed limits (sometimes under 20 mph) and some rural places have much higher speed limits. Highways tend to have higher speed limits, especially if they have no pedestrian access.
Most pedestrian deaths happen on arterial roads because the speeds are high enough to be dangerous/fatal, yet there are still many people walking and cycling.
I think your experience is common—people get upset about the government lowering speed limits to increase safety, but then after a few months it feels like it’s always been that way.
We've recently had some discussions on ~transport about the negative impacts of SUVs (among other things) on pedestrian fatalities. In short: statistically, large and heavy cars universally kill more pedestrians than small, light ones. But there's more to the story. Evidently, there are multiple factors at play! Just as much or more than weight, higher vehicle speed leads to more pedestrian fatalities:
Researchers are clear that larger cars are more dangerous. At a given speed, the force transmitted onto a pedestrian's vulnerable skeleton is inherently higher during a collision caused by a heavy vehicle than a light one. And the larger the vehicle, the worse the visibility for Vulnerable Road Users (VRUs), including pedestrians and cyclists, and especially children. In other words: big cars are bad for society.
However, above a certain speed, it doesn't matter how big the car is: pedestrians are going to die when hit. This includes speeds drivers frequently take on "arterial" roads, or larger collector roads that typically prioritize automobile throughput at the expense of pedestrian comfort. At speeds around 50mph, pedestrians have only a 10% chance of surviving being hit by a car. Hussain et al. 2019 conduct a meta-analysis of 20 traffic studies and determine that:
The study proposes that "high pedestrian active areas" should impose a speed limit not exceeding ~25 mph. But safety advocates want to ensure that this doesn't just affect local neighborhood streets, but also any higher-traffic arterial that might see pedestrians. The risk of death skyrockets between 20 and 40 mph, with the higher end of the range demonstrating a 50% fatality rate.
In the United States, it's common for arterial speed limits to be 45 mph or higher. Additionally, drivers routinely break speed limits, demonstrating a particular likelihood to exceed posted arterial speed limits in the minutes after exiting the freeway. This is commonly understood: whatever the speed limit, some number of people test it by 5–10 mph or sometimes more. It is therefore prudent to reduce speed limits beyond what they currently are, including on arterial roads. The only roadway which has no pedestrian interaction is a grade-separated or fully enclosed highway. On any other road, including arterials, it is essential to prioritize human life over traffic throughput, especially as pedestrian deaths are on the rise.
Going to have a slightly pedantic statement to disagree here.
There isn't more to the story or multiple factors at play. Larger, heavier vehicles are deadlier. Full stop.
Higher speeds are deadlier as well. But the two are independent of one another; if nothing else changed except the replacement of every SUV/CUV with a Camry, the number of lives lost would go down.
If nothing else changed except lower speeds, the number of lives lost would go down.
The factors involved aren't SUVs and speed. It's two independent factors that are worse when combined. SUVs have no purpose to the average driver that can't be solved by a smaller/lighter vehicle.
I've said it before, I'll say it again. Unless someone has the regular need to tow something of considerable weight while also requiring the accommodations of three rows of seating simultaneously, then they don't need an SUV and should be in a car or a van.
You have stated that there are multiple factors at play: one being weight, one being speed. Indeed, they independently contribute to pedestrian fatalities, but also amplify each other. Both of these metrics are important, which is what the purpose of this thread is.
I agree that there is no need for the majority of people to own a particularly large vehicle, including an SUV. Most states have a weight-based registration fee for automobiles, but it's a paltry amount. People really need to be charged thousands of dollars for registering an SUV, with tax credits or some other exception for people who can demonstrate a real need for the vehicles. Their danger to society is just too great.
My opinion is that the regulatory incentives to build larger SUVs need to be reversed. In the US at least, automakers are indirectly incentivized to produce larger SUVs due to the structure of fuel economy regulations.
The CAFE standards established in 2012 introduced a size-based efficiency curve. This meant that larger vehicles, like SUVs and light pickup trucks, had fuel efficiency targets that got relatively less stringent the larger the vehicle got.
Consequently, when faced with regulations meant to improve the fuel efficiency of their existing vehicles, automakers chose to instead increase the size of SUVs and trucks to fit a more lenient part of the curve.
I have to respectfully disagree with that idea. That seems like a way of saying "the wealthy can have it no matter what, but the poor can only have it if they need it." I'm not saying that SUV's should or shouldn't be regulated, as I don't really have an opinion on that, but wealth should not play any part in the regulation.
Ya know, completely off topic, but I find it burdensome to have to consider socioeconomic implications every time literally anything needs to be implemented. Hear me out before you consider me an uncaring asshole.
There's lots of issues where ultimately the solution, the problem, or anything in between is that "things get expensive" or that the distribution of prices changes, or what have you. Energy crisis in Europe? Well, the poorest won't be able to compete on price, so won't be able to heat their homes. Make trucks more expensive to dissuade people? Now the poorest won't be able to buy SUVs. I won't bore you with more details. Anytime one of these issues comes up, there's socioeconomic considerations inserted into the discussion, even though in principle the topics have nothing to do with socioeconomics. This makes a lot of these discussions endlessly tiring. And I'm not a fan. Ultimately, socioeconomic issues should be solved independently: Tax rich people more, give nonmonetary and monetary assistance to poor people. Once that's in place to an acceptable degree, making SUVs more expensive, or taxing CO2 emissions, or what have you, becomes much simpler, as the social issue isn't overshadowing whatever you're trying to fix. Giving poor people an SUV tax break, or an energy tax break, or otherwise omitting them from these financial tools we're using to shape collective behavior is (1) socioeconomic policy in varying degrees of disguise (2) weakens the policy wrt. its intended goals and (3) makes the implementation of that policy much more complicated. (e.g. in this case by bloating the number of tax breaks available - btw, this complexity benefits the rich)
Make social policy stay in its lane, and make it sufficiently strong that you don't have to worry about it every damn time you touch literally anything.
I'm well aware that as long as such a sound baseline of socioeconomic policy isn't in place, we have to consider side effects of policy, but man things could be so much simpler.
I think you've slammed the nail on the head with what I've failed to articulate lately. "SUVs are more dangerous and should be taxed by weight to discourage the purchase of them." "But then poor people couldn't buy SUVs!"
As if we were arguing over the 'right to run over pedestrians' as opposed to the right to scoot about town in three tons powered by explosions while staring at your phone. Yeah, poor people can't afford a lot of things, still doesn't make SUVs a necessity. Not like the truly economically disadvantaged are the ones buying them as opposed to getting run over by them while walking to the bus.
Your sentiment is noble, and I agree that it would be nice to find a solution that is not based on income. What is your proposal to equitably decrease SUV use across the board?
I feel like a license class for an SUV would be appropriate, similar to class A and B licenses that require extra learning and proof of ability to drive the larger vehicles. There are different rules that should be used when driving an SUV compared to a sedan and these should definitely be part of it. Drivers should be educated on, and be able to demonstrate abilities related to, larger gaps between vehicles at speed, different emergency maneuvers to prevent roll overs, dealing with larger blind spots on the road and in parking lots, and towing/cargo management. I think just adding a required license would cut down on the number of SUV drivers and improve the overall capabilities of the licensed drivers.
I agree that more licensing would be a good solution to cut down on SUV use. (I would still favor exaggerating our weight-based fees, because those remaining drivers are still contributing negatively to the safety environment, but maybe it could be a bit lower to account for the decrease in SUV use induced by a license.)
Do you think that more licensing could work politically? Should it apply retroactively, or just moving forward?
If by "politically" you mean acceptance by society, I would say that there would be uproar over it but it has been done before (since we do have licensing requirements in every state). I definitely think it would be a hard sell to any politician because of the impact it could have on their political careers and that it would be the next political hot topic because of how many people it would affect. If it actually made it to a vote then the opinions of the citizens should certainly weigh heavily on the vote.
I don't personally like the idea of retroactively applying laws, especially when it is something that is so heavily tied to a household's finances. I would have to say it should only apply moving forward. I know that means the problems created by SUV's would decline more slowly, but there has to be a balance between creating a safer environment and people being able to maintain their financial livelihood.
I’ll come back and say we can address that by increasing the tax burden on luxury.
So a tax based on weight, and a second tax based on msrp, where the tax increases exponentially as price increases from 33rd percentile.
The obvious follow-up question to the existence of this lethal velocity is "What is the lethal velocity of SUVs vs that of smaller cars?" If smaller cars are safer for pedestrians, isn't it a guarantee that SUVs simply reach that lethal speed sooner? I mean, it sounds to me like the two discussions (car size vs car speed) are more or less orthogonal in the sense that both increase lethality, but there's no unexpected interactions. That this lethal velocity exists, at which point the vehicle type doesn't make a difference, doesn't mean that vehicle type is unimportant.
Or in other, slightly cynical words: Given a certain tolerance of lethality (including zero), the speed of traffic could be higher if everyone just drove sensibly-sized cars.
I had the same question. The 2019 study I linked appears to analyze all motor vehicles, including sedans, SUVs, vans, light trucks, and probably heavy trucks. The figures shown would therefore appear to be averages based on 2019 usage data for each of these vehicle classes. Maybe you could do some speculative weighting math to figure out how the proportion of ownership of vehicles of a particular weight class affects those averages.
Paulozzi 2005 states:
The relative risk factor is compared to a baseline of 1, so in this case the risk of fatality per vehicle mile traveled (VMT) is apparently 1.45 for light trucks for the general population. But that is not strictly the metric we're looking for, because it evaluates overall danger based on overall usage (which could be influenced by various other behaviors independently resulting from differences in absolute distance traveled) rather than danger of one type of vehicle vs. another at a particular speed. So I don't think you can use the relative risk of fatality for a particular vehicle class shown in this study to directly calculate optimal speed limits for each vehicle class.
As a rough approximation that would probably infuriate real statisticians, maybe you could use that relative risk of 1.45 to enforce a 45% lower speed limit everywhere. Or maybe you could weight it to the portion of vehicles owned which are SUVs and apply that resultant speed limit (so, idk, 20% lower, I'm not doing that math) everywhere. But that's probably an excessive reaction considering buses have an RR of 7.97. (What are you going to do there? Enforce a 0 mph speed limit?)
Monfort et al. 2020 state:
...but I can't access the article to read the actual speed statistics.
Kröyer 2014 suggests that SUVs are also more dangerous at a given speed (I assume), and offers several remarks about other factors that influence the dangerousness of SUVs beyond weight alone:
The article doesn't explicitly analyze what a "safe speed" is for SUVs vs. sedans, but you can roughly and unscientifically extrapolate that what constitutes a "fatal injury" for an SUV collision with a pedestrian might be approximately equivalent to a "severe [but non-fatal] injury" for a sedan collision. This particular study states that a fatal pedestrian injury occurs when the offending vehicle has a mean speed of 48.9 km/h (30.4 mph) and a severe (but non-fatal) injury occurs when the offending vehicle has a mean speed of 40.5 km/h (25.2 mph).
So you might be able to say, as a quick approximation (because I can't find a study that answers this specific question with specific numbers for different vehicle classes), that driving an SUV is like driving a sedan 5 mph faster; or that an SUV driving at 25 mph would kill a pedestrian whereas a sedan would only severely injure them. But again, that is not explicitly what this dataset says, that is just a rule-of-thumb extrapolation I've made for the purposes of this discussion.
In any case, the fact remains the same: high speeds kill. Because some vehicles on the road are always going to be fairly large (whether SUVs, vans, or delivery trucks), it is worth considering this factor when choosing which speed limit to enforce on a particular street.
I mean, some cars have good excuses for being dangerous: I reckon busses are so dangerous because they're by definition close to pedestrians, and are also by definition heavy. That's a target rich environment. (If I'm right about the reasons there, I expect busses to have mostly excess slow-speed collisions compared to trucks.) Heavier trucks have the "excuse" that they are actually using all of that extra weight to lug around heavy goods. SUVs have none of these excuses. I could see, for example, a rule where vehicles in a certain weight class have to stay X below the speed limit. >2t? 5 under you drive. >5t? 10 under. Well, I could see this from a risk management perspective. The traffic flow implications are atrocious. Alternatively, a pressing need to operate such a heavy vehicle could somehow be required implicitly or explicitly. Special license required for heavy vehicles that's extra work to get? Suddenly only professional drivers with heavy goods will only find heavy vehicles appealing, as opposed to small people with big egos. Whatever cutoff you choose there for what is a heavy vehicle is then the standard for the purposes of speed limits. If 2t vehicles require special licenses, then you design roads s.t. 1.99t vehicles are slow enough not to kill pedestrians too often.
You can use momentum (mass x velocity) or kinetic energy (0.5 x mass x velocity^2) to compare the combined mass and velocity. It's more a simple physics modeling problem than a statistical one. At best, given the same velocities, a more massive object scales the output figure linearly. And when we're talking 5000lb SUVs vs 3500lb hatchbacks, that's very significant.
I don't think a linear relationship holds, especially since not all velocity is expended during a collision with a pedestrian. A very light vehicle that actually slows down due to the collision, sure, more or less linear there. But once the vehicle is so heavy that it actually doesn't appreciably slow down due to the collision, you might as well consider the mass infinite and be more or less correct. At which point all the soft factors mentioned by scroll_lock come into play. So I don't think it's weight per se that kills, it's just that it makes all the soft factors worse. But if you doubled brakes, engine, and weight of a given car without changing the dimensions or anything else, I don't actually think it'd make a noticeable difference. The difference would be that the car slows down from 50 to either 48 or 49 mph due to the collision, and that's it.
Yes, though as some of the research notes, the physical design of an automobile (especially its grill, which is what comes into contact with pedestrian victims) has an effect on pedestrian fatality rates. SUVs have different characteristics than sedans beyond weight. For example, whether they are likely to end up on the dashboard, flung to the side, or crushed below the wheels. Additionally, SUVs have lower visibility which affects the frequency of collisions with pedestrians in the first place. Factors like these influence the overall "danger" of a particular vehicle class, so it's still important to use real-world data where available.
I think your model can give us a pretty good sense of how driving a battery-electric vehicle (heavy) rather than an ICE vehicle of the same class might affect safety, though.
Yes. I've seen that concern a lot in the past, and it makes a lot of sense. If you stand next to a Camry or Fit, the car would hit you in the legs and you'd roll across the hood, which mitigates some of the force applied and keeps you out from under the car.
The typical SUV and contemporary truck strikes most people in the upper chest or head, and drives over them. So the way the kinetic energy is delivered is also worse than on a small vehicle...but either way, an SUV has a much higher KE at the same velocity, and even soemewhat higher velocities. Both are definitely an issue.
Having briefly rented a Yukon (because they had no minivan offerings for a road trip), it's also shocking how poor the visibility and maneuvering are. You pretty much need to rely on sensors and cameras for merging right or backing up, because there are so few spots that aren't blind it's ridiculous. You also would never see some or under five feet tall standing directly in front of the vehicle, and pedestrians at a crosswalk would easily be difficult in general.
I'm generally in favor of regulating SUVs out of existence and requiring a form of commercial licensing for pickup trucks, with heavy taxation.
I don't have time at the moment to read the article in it's entirety so perhaps you could answer a question: is a reason proposed anywhere for the actual increase? Speed kills, sure, but are cars driving faster now than 10+ years ago? Are more pedestrians walking on the stroads? Are more stroads being built?
The hypothesis championed in the article and by the report is "the suburbuanization of poverty" which basically means that there is an increased amount of pedestrians on stroads.
So it's not that there are more stroads or people are going faster, it's that more people walking along them now means more opportunities for the chance of a pedestrian collision.
That is what the report postulates. Technically, you can extend this concept as it relates to traffic safety to any area where there is a modal and/or demographic shift. Whether or not the change in the last 10 years is linked to poverty specifically (which I would believe, but can't definitively comment on), more people beginning to walk in an area that has traditionally had a lot of cars (and car-centric infrastructure) and few pedestrians means that there will be more pedestrian fatalities from collisions. Likewise, more people beginning to drive in an area that has traditionally had primarily pedestrian traffic can result in more people being injured and killed by motor vehicles.
That's an almost impossibly simplistic observation, and yet city officials do not necessarily incorporate reasonable safety measures along stroads and within neighborhoods that are seeing growth or modal shifts. Philadelphia's Washington Avenue, one of the city's most dangerous stroads, has seen a significant amount of residential development in the last few years. Yet despite all the anticipated foot and bike traffic, the city failed to properly implement a road diet, install protected bike lanes, and otherwise reduce driver speeds; what changes have been made are severely lacking.
As another example, this problem may be more evident in parts of the city's Northern Liberties neighborhood, which is right next to exits from I-95 and I-676, places where drivers are likely to exhibit highway-speed driving along what is technically an urban arterial. Callowhill Street near 2nd Street is nightmarishly wide and drivers routinely demonstrate reckless behavior there; this is despite the street dividing the neighborhood from the dynamic and lively Old City neighborhood. In other words, even though both Northern Liberties and Old City are growing rapidly, the city fails to redevelop around people; instead preferring a status quo which prioritize automobile throughput.
But this isn't a problem unique to Philly. City planners generally have good intentions—they're big on urbanist concepts and want communities to thrive. But through a combination of misinformation, inattention, and pressure from managers, consultants, or political appointees who are either not educated in urban planning or simply represent the interests of automobile users, many municipalities fail to make meaningful safety improvements to their streets. It is therefore important for constituents to be aware of the literal dangers of the status quo and to advocate for safer streets in community meetings and with their elected representatives.
Well, recently there was an accident when woman driving such car went over a kid in the town doing slow speed. Kid didn't survive. Why she ran the kid over? She couldn't see the first 9 meters ahead of her car frm driver's seat! Freaking 9 meters, that's 30 feet! If you can't see this distance in front of your car, something is not right. I'm not saying the car is the problem here. I'm saying that car makers making such cars are the problem. And small person sitting behind the wheel.
There was this image where SUV driver was saying how great the view from he car is sitting high above street level with kids playing in front of the car that were invisble to the driver. This is what just happened here, no more just a comic strip that wants to show the dangers, but reality.
Hi, as a person outside of US what the spees limit in the cities? Where I live recently (few years ago) govt provided new speed limit in city - 50km/hr, 30 mph. Previously it was 70km/hr, 43mph. First few months it feels slow, but now it feels perfectly ok.
As another commenter said, it varies greatly state-to-state. Wikipedia has an interesting list of speed limits by jurisdiction.
The Department of Transportation has some materials discussing types of places/roads that commonly use different speed limits.
In general—and this is very approximate—most neighborhood streets are superficially intended for fairly slow driving, perhaps around 20–25 mph. They are typically engineered for much faster driving, though—the streets are usually too wide, so drivers don’t obey the limits. (Sometimes, the limits are too high for a residential street, like 30–35 mph.) Very generally, the fastest posted speed limits within an urban area would be on an “arterial” road, probably at most 45–50 mph. School zones usually have very low speed limits (sometimes under 20 mph) and some rural places have much higher speed limits. Highways tend to have higher speed limits, especially if they have no pedestrian access.
Most pedestrian deaths happen on arterial roads because the speeds are high enough to be dangerous/fatal, yet there are still many people walking and cycling.
I think your experience is common—people get upset about the government lowering speed limits to increase safety, but then after a few months it feels like it’s always been that way.
This varies too much from state to state and even from city to city for me to feel like I can give a solid answer tbh