A quick set of remarks from mathematician/transit consultant Alon Levy on a pretty cost-effective way to improve rail travel times: smallish track realignments in “choke points” between sections...
A quick set of remarks from mathematician/transit consultant Alon Levy on a pretty cost-effective way to improve rail travel times: smallish track realignments in “choke points” between sections with otherwise high speed limits.
The axioms behind this blog post, which are not all directly discussed, are that:
Max safe train speed is limited primarily by how sharp the curve of its track is. The larger the radius, the faster the train can safely go. On most routes, the speed varies significantly from section to section for mainly geographical reasons, and as a result of existing development.
“If you want to go fast, don’t go slow” (railway saying). The best way to speed up travel times on a route is to make improvements to the areas where the train goes the slowest—not to increase its max speed at the fastest areas. (That is, work on slow points surrounded by similarly slow sections—not fast points surrounded by fast sections.)
Track realignments in urban areas generally require expensive land acquisition and demolition of adjacent structures (or tunneling/viaducts to avoid the issue), which can be untenable. By contrast, land acquisition is cheaper in rural areas, and there are far fewer structures.
$50 million is not considered a major expenditure for a single project on a rail route like the US Northeast Corridor (Amtrak), but $10 billion is an unusually large expense for a single project.
Thus the most mathematically optimal places to make rail improvements may not necessarily be the most cost-effective places (though they sometimes are).
Levy’s suggestion is that the second-best place to work on train speeds, after slow points surrounded by slow sections, is in slow points surrounded by fast sections. This reduces time wasted during acceleration/deceleration in that immediate area. And usually, the fastest track sections are also the ones in the most rural places, so it can be more practical to start working there from a cost perspective.
I look forward to reading whatever actionable report Levy and Devin Wilkins are working on.
A quick set of remarks from mathematician/transit consultant Alon Levy on a pretty cost-effective way to improve rail travel times: smallish track realignments in “choke points” between sections with otherwise high speed limits.
The axioms behind this blog post, which are not all directly discussed, are that:
Levy’s suggestion is that the second-best place to work on train speeds, after slow points surrounded by slow sections, is in slow points surrounded by fast sections. This reduces time wasted during acceleration/deceleration in that immediate area. And usually, the fastest track sections are also the ones in the most rural places, so it can be more practical to start working there from a cost perspective.
I look forward to reading whatever actionable report Levy and Devin Wilkins are working on.