By Road and Rail?

CygnusXII writes "Now this is a novel approach to Dual Mode Transportation. This is an interesting and refreshing approach, that could revolutionize the transportation industry. BladeRunner Dual Mode Transport, or see the main web page. The innovative vehicle will run on road as well as rail. It is as applicable to freight as to passenger transport. Branch-line infrastructure costs could be at least halved because signalling and points could be largely, if not totally, made redundant."

Comments

You don't know anything about railroads, do you?

[rfc1394]

Think about it.

you have a dual purpose buss rolling along a rail route at, ummm, what, 80kmph? It weighs, what? 10 tons? 20 tons? Then right behind it is a kilometer long train full of, oh, I dunno - NAPTHA - that's roaring along at what?140kmph? ANd it weighs how many hundreds of tons? And takes how long to stop?

A good rule of thumb for stopping distance is roughly 1 meter per kph in daytime, about 1 1/4 at night; I've heard that at 80kph (which is exactly 50mph for those of us in the States) the distance is about 81 meters (about 245 feet) and at night it's about 95m (about 300 feet).

And then Brer Rabbit pulls the STOP AT NEXT CORNER pull tab in the dual purpose bus, and while he's getting his geriatric bones off the bus, everyone is sighing and wondering WHEN THE HELL HE'S GOING TO GET THE HELL OFF THE BUS. And as he ever so slowly mosies off the bus BLAMMO! Hit from behind by a train full of naptha.

Not a chance. You don't know anything about railroads, do you? They already thought of this.

Every railroad operates on a "block" system. This is an interlock designed so that only one rail vehicle may enter an area of track at a time. At the start of each block is a red / green signal and either a speed limit sign or an automated transponder to tell the operator the maximum speed limit for the block they are about to enter. The area of a signal block is something large enough for a train to come to a complete stop, or if necessary, when a train enters a track the signal for the block it is in and the block before it (to allow for any train following it) become red. The faster trains run in an area the larger the block is (or the more preceding blocks are also interlocked). Once a train enters a block, the signal behind it at the entrance to that block turns red and stays red until they enter a new block or change to a different track. It may also cause the transponder in the block behind it to order approaching trains to reduce speed in case they get to their block before they are clear so that they won't have trouble slowing down if necessary. Only once it is completely clear of a block will the signal for that block turn green again. A train operator who sees a red signal will stop their train and not enter the block until it turns green, same as you will stop at a red light when operating a motor vehicle on a street.

An automated train will warn the operator that the next block is occupied and if he fails to bring the train to a stop and crosses the red signal anyway, it will trip the emergency brakes and the train slams to a stop. This is why it's said when a rail engineer runs a red signal he "tripped a signal." If the engineer enters a block at a speed faster than the transponder it will either apply braking or give a warning then trip. The rail system is designed to prevent this sort of thing from happening. This system is also in place in the event of rail fissures, there is a small electrical current running along the rail, if any rail comes loose, it breaks the connection and turns the block red so a train can't enter it, or possibly opens an earlier switch so trains can be routed around the block, I'm not exactly sure.

I do know that rail systems are specifically designed to prevent this sort of thing in the absence of negligence or intentional misconduct. If a train operator ignores signals in some cases they may be able to run red lights (on non-automated trains) but the scenario you describe can't happen except by intentional misconduct or flagrant negligence. Besides that

• if the bus was routinely stopping for passengers, obviously they'd pull off the track for that exact reason, so as not to disrupt the flow of trains not stopping there.
• a transport line - bus, trolley or train - runs on a schedule, and the stop times are accounted for in operating the line.
• the train usually has fixed amounts of time it waits at a stop in order to account for