How does SCOOT model driver behaviour?
Discussion
SCOOT is the automated, intelligent system that controls traffic light phasing in built up areas.
My local council is consulting on upgrading zebra crossings on all 4 arms of a small roundabout to toucan crossings, and have claimed it will benefit "all users" because their modelling in SCOOT has shown better traffic flow.
It may be true, but I'm sceptical about how the model simulates driver behaviour. A mile up the road there is a pelican crossing right on top of the exit of another roundabout, whch queues up right over the roundabout because drivers in the real world don't give way or leave gaps where they ought to.
Hence the question.
FWIW I'm prepared to keep an open mind about it, but would like to get some background.
Thanks.
My local council is consulting on upgrading zebra crossings on all 4 arms of a small roundabout to toucan crossings, and have claimed it will benefit "all users" because their modelling in SCOOT has shown better traffic flow.
It may be true, but I'm sceptical about how the model simulates driver behaviour. A mile up the road there is a pelican crossing right on top of the exit of another roundabout, whch queues up right over the roundabout because drivers in the real world don't give way or leave gaps where they ought to.
Hence the question.
FWIW I'm prepared to keep an open mind about it, but would like to get some background.
Thanks.
My knowledge of traffic models isn't the best, but...
SCOOT is an operating system. So, it can adjust the timing of traffic signals using live data once it is in operation. For example, if there are two sets of signals a hundred metres apart, it can time the 2nd set to go green when it calculates that traffic setting off on green from the first set should get there.
It isn't a traffic model. To understand whether a system will work better with different designs requires another application; ie a traffic model. The traffic model might use data retrieved from SCCOT.
As to the question, i guess - and it is a guess - that some of the more sophisticated traffic models might be able to model driver behaviour such as you describe.
SCOOT is an operating system. So, it can adjust the timing of traffic signals using live data once it is in operation. For example, if there are two sets of signals a hundred metres apart, it can time the 2nd set to go green when it calculates that traffic setting off on green from the first set should get there.
It isn't a traffic model. To understand whether a system will work better with different designs requires another application; ie a traffic model. The traffic model might use data retrieved from SCCOT.
As to the question, i guess - and it is a guess - that some of the more sophisticated traffic models might be able to model driver behaviour such as you describe.
Basic said:
My knowledge of traffic models isn't the best, but...
SCOOT is an operating system. So, it can adjust the timing of traffic signals using live data once it is in operation. For example, if there are two sets of signals a hundred metres apart, it can time the 2nd set to go green when it calculates that traffic setting off on green from the first set should get there.
It isn't a traffic model. To understand whether a system will work better with different designs requires another application; ie a traffic model. The traffic model might use data retrieved from SCCOT.
As to the question, i guess - and it is a guess - that some of the more sophisticated traffic models might be able to model driver behaviour such as you describe.
This. SCOOT is an operating system. So, it can adjust the timing of traffic signals using live data once it is in operation. For example, if there are two sets of signals a hundred metres apart, it can time the 2nd set to go green when it calculates that traffic setting off on green from the first set should get there.
It isn't a traffic model. To understand whether a system will work better with different designs requires another application; ie a traffic model. The traffic model might use data retrieved from SCCOT.
As to the question, i guess - and it is a guess - that some of the more sophisticated traffic models might be able to model driver behaviour such as you describe.
You can programme traffic signals to, say "a peak hour plan", and it will use that plan at that time, on that day or days of the week, until you change it. The plan is worked out using a model such as TRANSYT, which is better than it used to be, but still not very good at modelling how queues interfere with each other, so the modeller has to be very careful - especially at roundabouts - that you don't just accept the first answer that it comes up with. Queue formation and dispersal has to be checked carefully to make sure that the model is right.
There are other microsimulation models such as Paramics and VISSIM that model interaction between individual vehicles, so you can see queues and how they affect upstream junctions.
Either way, you first calculate a basic timings plan. What SCOOT does is introduce flexibility to that plan. It counts the amount of traffic as it goes, on a particular day, and adjusts the signals in tiny increments. So for example, if it counts that approach A is slightly quieter than "standard", but approach B is slightly busier, it will knock a couple of seconds off Green Time A, and add it to Green Time B. If the flows in the next cycle are the same, it will adjust by another second or two. If B is busier in the next cycle, it will adjust the green times back towards standard. It can also adjust the cycle time to optimise flow, and it can adjust the offset (the time that signals at junction 2 change to green, after junction 1). So at the end of the peak, depending on the flows, you might be back to the "standard plan" or you might have timings that are a lot different.
What it won't do, is miraculously solve a problem if queues are interfering with a junction back up the line. What it also won't do, is model how often, and for how long, an unsignalled zebra crossing stops traffic - that is a variable that SCOOT cannot take into account.
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