Comment by thanzex | Hacker News Reader

Comment by thanzex | Hacker News Reader

Parent Full thread

I think that's not something that can be avoided, unfortunately. Any number of things could cause a train to suddenly stop. A mechanical failure, derailment, collision, a wagon could get detached... On roads we have millions of vehicles, carrying on average a very small amount of people, around 1.5. For efficiency sake we have accepted the risk of staying within reaction distance instead of stopping distance between vehicles.

It is a tradeoff between the safety of lives on board and traffic requirements that is relatively easier to accept when the average number of people involved is low against massive speed and efficiency gains.

The same cannot be said for trains though. Modern trains carry upwards of 1000 passengers, often at high speeds and without all of the safety and retention systems built into modern cars.

Having one or multiple trains with this large amount of people onboard be involved in a sudden catastrophic accident is possibly not worth the efficiency gained by thess than one minute separation.

Unfortunately we cannot just think about a normal scenario of simple deceleration

> On roads we have millions of vehicles, carrying on average a very small amount of people, around 1.5. For efficiency sake we have accepted the risk of staying within reaction distance instead of stopping distance between vehicles.

No. Unsafe drivers have illegally decided this, but in most jurisdictions it is your responsibility to stop your vehicle short of the one in front of you. You should be maintaining stopping distance from your vehicle to the one in front.

> You should be maintaining stopping distance from your vehicle to the one in front.

I am not so sure. In Germany, for example, the minimum required distance to the car in front of you is "speed in km/h divided by 2 in meters". So for 100 km/h, you are required to keep a minimum distance of 50 meters. I very much doubt that you can stop a car going 100 km/h within 50 meters.

You do t need to stop a 100 km/hr car in 50 meters because, barring that sudden brick wall appearing ahead of the car in front of you, they’re not stopping in 50m either.

The 50m is the reaction buffer, not the stopping buffer.

It’s also prudent to give more leeway to vehicles you can not see around to avoid the large truck swerving to avoid the refrigerator that just fell out of the truck in front of them problem.

At least with cars they also have the option to swerve away from the chaos if the stopping distance is too short.

Not to disagree, just throwing in a variable that trains don't have

That's interesting, in Belgium I think it's "2 seconds", or at least that's what was promoted recently on the radio.

You should be able to sing "Last night a DJ saved my live", which is a bit more than 2 seconds. I liked that, because it's one you can actually test for while driving.

I find it a lot harder to estimate 50m while driving at 100km/h

The reflector posts are always exactly 50 meters apart, which makes this relatively easy.

Not really. In my country, at least, it is explicitly stated in driving theory manuals to maintain at least one reaction distance between the car in front of you.

For a car traveling at 100Km/h the stopping+reaction distance would mean more than 130m, which is a quite large and possibly impractical for higher traffic scenarios.

Reply on news.ycombinator.com