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Need a PhD Topic? How about cops in traffic

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Re: Need a PhD Topic? How about cops in traffic

#11

Post by pbhjpbhj »

mattmanser wrote: post #8
larrydag wrote: post #4

Earlier quoted context omitted.

I could see this being possibly useful in traffic "wave" disruption. I've read on the traffic wave theory before and there has been some ideas that if the wave could be disrupted long enough to clear out that it would dissolve and traffic would start to flow again at its normal pace. I suppose that disruption could be done by police cars allowing buffers to build thus disrupting the wave. Can you tell I find this fie…

Sans the copper, they do this over here in the UK by using variable speed limits, hard shoulder 'opening' and the real threat of speed cameras. Seems to work in my albeit anecdotal and very occasional experience of driving near Birmingham in rush hour. Would be interested to hear the perspective on UK HNers who were aorund before/after they implemented this. And they're using it more and more: http://www.bbc.co.uk/ne…

I must say I've long assumed that they also used police cars for flow control - now of course they have the Highways Agency vehicles¹ which look so much like police cars as to cause the same slowing to ---

¹ -- I can't see how the Highways Agency are not running fowl of the law against "impersonating a police officer" by the livery of their vehicles.

Re: Need a PhD Topic? How about cops in traffic

#12

Post by larrydag »

pbhjpbhj wrote: post #11
mattmanser wrote: post #8

Earlier quoted context omitted.

Sans the copper, they do this over here in the UK by using variable speed limits, hard shoulder 'opening' and the real threat of speed cameras. Seems to work in my albeit anecdotal and very occasional experience of driving near Birmingham in rush hour. Would be interested to hear the perspective on UK HNers who were aorund before/after they implemented this. And they're using it more and more: http://www.bbc.co.uk/ne…

I must say I've long assumed that they also used police cars for flow control - now of course they have the Highways Agency vehicles¹ which look so much like police cars as to cause the same slowing to --- ¹ -- I can't see how the Highways Agency are not running fowl of the law against "impersonating a police officer" by the livery of their vehicles.

Notice how truckers work with highway congestion too. They tend to slow down to allow congestion in front of them to flow. This might look at first to allow braking space for the big trucks but I think it has a lot to do with the traffic flow as well.

Re: Need a PhD Topic? How about cops in traffic

#14

Post by yummyfajitas »

acslater00 wrote: post #10

As it happens, I studied traffic flow back when I was an undergrad in the context of "agent based modeling". Agent-based models are basically computer simulations where you throw N 'agents' into an environment with pre-defined rules and then watch how they interact with each other. This setup lends itself perfectly to vehicle-flow; each agent is a car, each car has a model for when it accelerates, when it slows down,…

I don't think you need agent models. You can probably study this directly with the nonlinear transport equation (Lighthill-Witham, I think), or one of the more detailed versions (the Rascall model?).

All you need to do is impose a police-created boundary condition at x=cop_location(t) instead of solving the pde on free space:

    velocity(density)|x=cop_location(t) = cop_velocity(t).

Re: Need a PhD Topic? How about cops in traffic

#15

Post by noedig »

I saw something like this the other day at a stop sign. Normally there is a lot of traffic going through this stop sign at rush hour, but it doesn't get backed up. The other day there was a police car sitting near the stop sign. It caused a huge backup that stretched for several blocks. Turns out people were being extra careful to come to a complete stop for a few seconds because of the police car, and that caused the line to move more slowly than normal.

Re: Need a PhD Topic? How about cops in traffic

#17

Post by sumbry »

larrydag wrote: post #12
pbhjpbhj wrote: post #11

Earlier quoted context omitted.

I must say I've long assumed that they also used police cars for flow control - now of course they have the Highways Agency vehicles¹ which look so much like police cars as to cause the same slowing to --- ¹ -- I can't see how the Highways Agency are not running fowl of the law against "impersonating a police officer" by the livery of their vehicles.

Notice how truckers work with highway congestion too. They tend to slow down to allow congestion in front of them to flow. This might look at first to allow braking space for the big trucks but I think it has a lot to do with the traffic flow as well.

Truckers don't like to change gears. It's much more efficient for them to stay in a lower gear and coast at a consistent speed than it is to constantly change gears and brake.

Re: Need a PhD Topic? How about cops in traffic

#18

Post by politician »

yummyfajitas wrote: post #14
acslater00 wrote: post #10

As it happens, I studied traffic flow back when I was an undergrad in the context of "agent based modeling". Agent-based models are basically computer simulations where you throw N 'agents' into an environment with pre-defined rules and then watch how they interact with each other. This setup lends itself perfectly to vehicle-flow; each agent is a car, each car has a model for when it accelerates, when it slows down,…

I don't think you need agent models. You can probably study this directly with the nonlinear transport equation (Lighthill-Witham, I think), or one of the more detailed versions (the Rascall model?). All you need to do is impose a police-created boundary condition at x=cop_location(t) instead of solving the pde on free space: velocity(density)|x=cop_location(t) = cop_velocity(t).

Would that model take into account the number of lanes and the lane position of the cop?

Re: Need a PhD Topic? How about cops in traffic

#19

Post by Splines »

ed209 wrote: post #13

Here's a brief demo [video] of how these jams can start for no apparent reason http://www.youtube.com/watch?v=Suugn-p5C1M

It must have taken careful coordination to get them into the starting position too.

I'd be interested to see videos of solutions they've come up with. They could even try solutions that exist today (variable speed limits, hard shoulder openings, ramps with traffic lights when adding cars, etc.).

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