High Speed Trains

what technology makes the high speed train goes very fast unlike conventional trains?

* Better track. Pretty obvious, huh?
* More power. Faster you go and the heavier you are, the more power you need. The more Kw per seat, the better.
* Better signalling. Most of the world tends to agree that not crashing is a Good Thing(tm). This generally meanms cab signals, automagic stops, and PTC / or modified signal rules.
* Above 125 or so - no freight on the same tracks, period. Freights tear up the track and beat it out of shape. Even an overweight train like an Acela is nothing Vs a freight.
* Light weight. Weight directly effects track maintenance and operation costs, period.
* Better suspension/trucks. Most HSTs have body mounted motors, special trucks, and more and more hollow axles. The trick is to get the speed at which the truck self oscilates (hunts) to be significantly higher than the max speed. Supposedly, the TGV has a safety margin of over 100mph without the use of dampers, here. The Acela has effectively a negative margin - without dampers it hunts even in the normal operational range.
* Electric traction. Almost a requisite, or you get killed on power costs and suffer bigtime on acceleration. Expect 12.5k or 25k at the wire although 15kv 16.3 hz and even 3,000 volt DC has been used on the TGV. Few diesels are light/powerful enough, turbines aren't efficient or low maintenance.
* Brakes! Multiple discs per axle and dynamic or regen. once again, heat increases with speed and weight.
* Steep grades. The things that make an HST go fast also mean it can climb a 4% grade with ease. Makes planning/building lines easy. But...
* Fewer curves. ...Curves are an issue even with tilt technology, which adds weight while also imposing even stricter weight limits. The highest unbalance used in the world is in Germany (11+inches!) where the track/train has to be specially certified and the loading is so critical the train is weighed en route. 7 - 9 inches is more practical, but demands high maintenance standards and good equipment (FWIW, the X-2000 ran it in service in the US. The Acela still doesn't and likely never will).
*Grade sepparation. Required above 100mph or so, but where speeds are lower, not required, but useful still.
* Precision maintenance. Using a hammer to 'make it fit' and ignoring the roadbed is bad bad bad. Once again, light weight drops these costs dramatically.

Nasadowsk wrote: * Electric traction. Almost a requisite, or you get killed on power costs and suffer bigtime on acceleration. Expect 12.5k or 25k at the wire although 15kv 16.3 hz and even 3,000 volt DC has been used on the TGV.

15kV, 16,75 Hz is the standard on german high-speed-lines (HSL) as on all electrified mainlines in Austria, Switzerland, Sveden and Norway.

The TGV-Network uses 25kV, 50Hz on its HSLs but there are a few stretches with 1500 V DC!!!
Also Spain, Belgium, the Netherlandes and since a few years Italy use 25kV, 50Hz on new built lines and HSLs.

3000V = on HSLs exists only in Italy.

On normal or rebuilded lines (speeds betwenn 90 and 140mph) also TGV and ICE uses 1500V DC and 3000 V DC (ICE in the Netherlandes and in Belgium, TGV in France, Italy, Belgium).

Grade crossings can be a challenge. One method is to have four gates, that totally block all four sides, so drivers won't drive around. This also requires a certain amount of stationary barriers, so drivers won't drive on shoulders, sidewalks, etc. Also, this requires cooperation from local police as far as ticketing, etc., to avoid a culture of sloppy enforcement.

Crossings have to be flat, so that long trucks won't high-center and get stuck.

In remote areas, crossings need to be offset, such that a drowsy driver won't cruise on thru, but has to curve slightly to keep on the road. Of course, you don't want the drowsy driver to hit a brick wall, there needs to be room for a sand pit.

In cities, alternate streets can be one-way streets, to achieve a four-way effect.

Private, ungated crossings are pretty much unsuitable. In some areas, a few private crossings can be combined, with collecter roads on each side. In other cases, low-cost Bailey Bridge overheads can be implemented. Or, a low clearance (8 foot) undercrossing is possible. With a locked gate for bigger trucks.

modorney wrote:Grade crossings can be a challenge. One method is to have four gates, that totally block all four sides, so drivers won't drive around. This also requires a certain amount of stationary barriers, so drivers won't drive on shoulders, sidewalks, etc. Also, this requires cooperation from local police as far as ticketing, etc., to avoid a culture of sloppy enforcement.

Crossings have to be flat, so that long trucks won't high-center and get stuck.

In remote areas, crossings need to be offset, such that a drowsy driver won't cruise on thru, but has to curve slightly to keep on the road. Of course, you don't want the drowsy driver to hit a brick wall, there needs to be room for a sand pit.

In cities, alternate streets can be one-way streets, to achieve a four-way effect.

Private, ungated crossings are pretty much unsuitable. In some areas, a few private crossings can be combined, with collecter roads on each side. In other cases, low-cost Bailey Bridge overheads can be implemented. Or, a low clearance (8 foot) undercrossing is possible. With a locked gate for bigger trucks.

No. Because grade crossings must be close early enough to give a signal to the train before he comes nearer than the distance he needs to stop.

This means on HSL like Paris - Lyon where 30 trains a hour can go in both directions that in the rush hour the gates would never be open...


And also four gates cannot eliminate the possibility that cars stop on the rails ore have accidents between the gates...

So try to imagine a 320km/h (200mph)-Train has a crash with a 40 metric-tons lorry.... not good.

modorney wrote:Grade crossings can be a challenge. One method is to have four gates, that totally block all four sides, so drivers won't drive around.

On genuine High Speed Lines there can be no crossings at all, anywhere. If you are building a new line there is no problem about building bridges wherever a road needs to cross the track. There can be no farm crossings at all.

If a high speed train is running on a conventional line it cannot go at full speed.

Even on the Acela lines (not genuine high speed) I have seen a foot crossing that has been locked off and a tunnel provided to replace it (near Point o' Woods in Connecticut).