The alignment Downtown is grade separated. I would be fine with it in a subway, but I think the tunnels and various other underground construction would make that pretty difficult. The guideway can fit just fine running over the street, and running between buildings isn’t a problem – just slow down through downtown.

Aesthetically speaking, it’s possible to do a very nice job of building an elevated system in a downtown environment.

I stayed in Taipei for about a month a few summers ago, and I had a lot of fun checking out the elevated system they have through much of the city. It’s done very nicely: it’s way up high, it provides shade (but doesn’t make it too dark), and they’ve used the space underneath as a sort of pedestrian plaza with shops and fountains and things – it really is a very enjoyable retail colonnade or sorts.

So the answer is, it could be either. My gut feeling is that elevated is a lot more realistic, but I certainly recognize that a tunnel would probably be less controversial.

Well, I’ll keep that in mind, but for the purposes of this example I’m not going to try and revise the numbers. I don’t have the time or the engineering data to model it much more accurately than I have already. I’ll make a note on future posts in the series reflecting some of the factors you’ve mentioned that aren’t in the model.

@KP,

I might include a spur into Texas City, but I’m a little more inclined to suggest some kind of high quality BRT circulator to connect to Downtown TC and the TC Industrial complex.

In the short term I have no feel for how much traffic would go back and forth from central Houston or Galveston to those destinations – Texas City is really a very self-sufficient city.

To implement the BRT, I’d improve Palmer / 9th to a multiway boulevard configuration. That strikes me as offering much greater local benefit than a second train station in the near term.

As the city grows – and especially if there ever is a major anchor downtown (like a major redevelopment effort around the Dike), then maybe that BRT circulator route could evolve into a rail spur.

thanks for answering my questions. Please note that acceleration is typically not constant. Wind resistance increases with the square of velocity, so the closer you get to a vehicle’s top speed, the smaller the amount of additional acceleration you can still achieve. Ignoring this means your results are either way too optimistic or the vehicles have to have stupendously powerful motors.

Note that in steel wheels technology, trains are limited to 150mph if the tension on the overhead catenary system is just 3kV. For higher speeds (or high acceleration at high speeds) higher voltages are needed. Most of the NEC uses 12kV, Germany/Switzerland/Austria uses 15kV, more modern dedicated HSR lines use 25kV.

The AMT system appears to use a third rail pickup, those are typically limited to 1500V and suitable for top speeds of around 80mph – no more. You might want to ask AMT exactly how their propulsion system works before parroting their claims of 150mph top speed (extremely unusual for regional/commuter service).

A secondary issue is that discontinuous jumps in acceleration should be avoided. You need a few seconds of ramp-up and ramp-down to optimize passenger comfort.

To calculate travel times I worked the following math…

Max Speed

Acceleration

Time to Top Speed

Distance to Top Speed (Remember Vo is zero)

The forumla is then basically the same as what you typed.

If the distance is more than 2x the acceleration distance, take whatever is more than 2x the acceleration distance and divide by the speed to get time, then add the twice the acceleration time to top speed.

If the distance is less than 2x the acceleration distance, take the half the distance, calculate the travel time at the given acceleration rate, and double it.

In all cases I added 20 seconds at the end of each segment for stop-time.

If I can figure out a way to put that in JS on the web, I will.

First, I have no relationship with AMT. I have enjoyed meeting their President, Tony Morris, who was helpful when I was working on my thesis research. I like their technology because I like it, and I’m imagining it in operation in Houston because this is my blog, and I can.

As I posted on your last comment, I used an acceleration rate of .15g and a top speed of 150MPH. I did not account for curvature of the track for two reasons:
1. The only place where tight curves are likely required is on the approach to urban stations, and usually you’re decelerating already in order to stop. On many of those segments there isn’t room for the train to hit much over 50 MPH anyway.
2. The track should be designed for speed. I didn’t engineer it, I just sketched out a route. When the engineering work is done that alignment should be configured so that the train is traveling as fast as possible, and as close to even, uninterrupted acceleration and deceleration as possible. That certainly won’t happen in every instance, but until the engineering is done it’s not worth the time to try and guess what compromises will have to be made and how much they’ll affect the travel times.

You’re right about the option of express and semi-express services, those would significantly reduce travel time. For this particular post I’m still looking primarily at regional commuter service, however, so the number of stops is what I think is appropriate for that service. The route should be built so that it is capable of handling both kinds of service simultaneously (probably triple or quadruple track in certain areas). I’ll look more at what some express travel times might look like later in the series.

@Rafael, in “Texas High-Speed Rail: Houston – Part 1″ Andrew puts the distance to top speed as 1500 meters.

I did my calculations in Excel but here they are in js:

//milesDistance is the distance from one station to the next
topSpeed = 150;
milesToTopSpeed = 0.932056788;
milesAtTopSpeed = if(milesDistance>(milesToTopSpeed*2)){milesDistance-(milesToTopSpeed*2)}else{0}
milesBelowTopSpeed = if(milesDistance<milesToTopSpeed*2){milesDistance}else{milesDistance-milesAtTopSpeed}
minutesTravelTime =((milesBelowTopSpeed/(actualTopSpeed/2))+(milesAtTopSpeed/topSpeed))*60;


two requests:

(a) please clarify your relationship, if any, with AMT Corporation. If you have none, your thoughtful posts should perhaps focus more on the transportation requirements/opportunity.

There are lots of proven rail transit systems featuring full grade separation, including funky stuff like suspended monorails. Don’t start with the solution and go looking for a problem..

(b) can you elaborate on the acceleration profiles you use to estimate line haul times between stations?

(c) local-only service is ok for a 10-mile line. Galveston is over 50 miles from Houston, you may want to consider offering semi-express service level with just half a dozen intermediate stops in addition to local trains. That implies reliable operation to a timetable and bypass tracks at stations with low boarding/alighting numbers. Keep in mind that a low line haul time between the downtown areas depends on high average speeds. Trying to compensate for frequent stops with high acceleration and high top speed is expensive and inefficient.