David Benton wrote: ↑Tue Mar 30, 2021 6:39 pm
I guess diesels 110 mph trains could operate under the wires of a HSR system . I think this approach is suitable for the USA. There is an article in the Railway Gazette international that describes single track HSR development as well. In short , it may be better to have longer intergrated sysytems , rather than isolated Full HSR for the USA.
The French did this with the original TGV, using existing 100 mph conventional track into the cities. Vs the Japanese who went with a dedicated . isolated bullet train line. To the extent of been a different gauge to the existing system .
110 mph trains running on the same tracks as 220 mph trains is a disaster in the making, assuming they are going 110 mph instead of 79 mph. How long does it take a train to go 10 miles, about the average distance between control points?
At 220 mph (your typical HSR speed), it takes 2.7 minutes to go 10 miles.
At 110 mph (your typical higher speed diesel powered intercity rail speed), it takes 5.4 minutes to go 10 miles.
At 80 mph (your typical commuter rail speed), it takes 7.5 minutes to go 10 miles.
At 50 mph (your typical freight train speed), it takes 12 minutes to go 10 miles.
At a maximum on tracks being shared with freight trains, you can only run 5 trains/hour over the track, a train every 12 minutes.
If you want the trains to go faster than approach medium speed on a typical track block signaling system, halve the trains so their is an additional track block in front of the HSR train. Now we are at a train every 24 minutes, less than 3 trains per hour. Of course, after 3 minutes your HSR train will have to proceed at approach medium speeds until the freight trains pulls over into a passing siding. There are many valid reasons why some HSR operators run their trains on dedicated tracks.
The Japanese use dedicated tracks and moving blocks signaling systems, which is how they achieve HSR trains running with headways of less than 3 minutes over the track.
That is also why HSR trains slow down to 79-110 mph on shared tracks with freight trains.