Reply to post: Re: good distances between cars is just good for overall traffic flow

Back seat drivers fear lead-footed autonomous cars, say boffins

Anonymous Coward
Anonymous Coward

Re: good distances between cars is just good for overall traffic flow

At 70mph more than half of it is reaction time. As you slow down that percentage increases.

My car can stop in its own length at 30mph, but it'll travel around 2 lengths in the time it takes to get off the throttle and onto the brake.

With automation you could not just lose the reaction time - you could also do a proximity scan and discover the car before the one you're following braking, giving you more margin to do it smoothly.

However, I would like to remind you of the problems when ABS was introduced. From personal experience, I know that if YOU manage to stop in time it doesn't mean the car behind you can as well. A human following an automatic vehicle ought to leave quite a bit of distance.

There is another problem here - those who suggest that we should drive vehicles in the sort of short-distance "trains" that, for instance, VW was demonstrating forget two things:

- the fuel savings because of reduced wind drag don't really apply to city speeds;

- you are creating the equivalent of the bendy bus that made a complete mess of London's traffic until the next mayor finally got rid of them (unless you find some algorithm that breaks up these trains when required).

There is possibly a violation of traffic laws at play: normally, you are required to leave enough space between vehicles for another one to move in (at least on a motorway). Granted, few do that (which is why you get a queue a mile long when there is somewhere an overtaking HGV in sight), but that is the actual law, designed to ensure there is an escape hatch for idiots screwing up an overtaking manoeuvre (at least that's what I think it's for). In a city, traffic flows best too if you are occasionally polite and let someone come out of a difficult spot. I'm not confident a vehicle train can be programmed to do the same.

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