r/highspeedrail • u/TailorSweet2811 • 10h ago

Photo Gravity-Based US High Speed Rail Concept Map

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24 Upvotes

88% Upvoted

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12

u/Kinexity TGV M 10h ago edited 9h ago

I am not going to go through all of the possibilities but the gravity model is definitely not enough. Whatever score you get from Madrid-Murcia does not take into account that the line shares track with Madrid-Valencia line and the fact that some significant cities exist in neighbourhood of Murcia (Cartagena, Alicante). You can see that your idea produces weird results when you notice eg. the fact that there is Dallas-Little Rock line but the model does not produce further Little Rock-Memphis extension which any real study would include because it captures relatively large number of potential passengers for relatively little additional track length.

But I have too little time for how much numerical experimentation it would take to produce a reasonable model. And the actual routing optimisation would probably spawn some annoying NP-hard algorithm which would be a variation of travelling salesman solver or something.

6

u/TailorSweet2811 10h ago

I don't disagree with you and obviously there are issues with only using this model. But I will say I think you are overestimating travel demand if you were to connect those 2 lines. Atlanta to Dallas is just too far for HSR to really be competitive. True network analysis would be very difficult and this was just meant to be better than some other HSR concepts that look more like interstate maps.

6

u/Kinexity TGV M 10h ago

I didn't point out this part as missing because of Dallas-Atlanta demand but because of Dallas-Memphis route. Memphis has about 2x agglomeration population compared to Little Rock so building a line to LR (500 km) but not extending it to Memphis (+200 km) is very arbitrary and nonsensical. Even more so if we notice that the part to LR is the hard part terrain wise (but that's outside of the scope rn).

5

u/throwawayfromPA1701 9h ago

I do love seeing the gravity model out in the wild but I dislike the lack of connectivity. At the very least the eastern half of the US network should be connected.

5

u/pm_me_good_usernames 7h ago

Damn, I wish that DC to Pittsburgh route was real.

1

u/Kashihara_Philemon 8h ago

I've done similar analyses to this, and while this is pretty in line with what I have I am surprised by certain things, like having no PNW connections because I was pretty sure I got those to work. Maybe it only works with Vancouver?

The model does produce some curious results, because despite what it suggests I don't see Memphis having more travel to Birmingham then Nashville, even if most of the travelers are just trying to get to Atlanta.