Cameras on the top of Traffic lights.

[Saxon]

Thats why flashing your lights at them in the right place can work a treat;)

And at the right frequency of course (which is very difficult to do!)

[speeed]

And at the right frequency of course (which is very difficult to do!)

 

Wondered why it only worked occasionaly and on certain lights!

Some seem to be easier than others to crack.

[Shazbat]

If they're meant to sense traffic, why is it late at night when I approach from the Gleadless Road/Daresbury junction the lights at Blackstock Road turn to red for me and green for Blackstock when there's NOTHING coming that way

[Ginner]

...some traffic lights have little cameras on top.... what are they 4?!

They are Microwave Vehicle Detectors.

 

Can't find any reference to them being reactive to Emergency Vehicles' blues.

[simondjuk]

They are Microwave Vehicle Detectors.

 

Can't find any reference to them being reactive to Emergency Vehicles' blues.

 

Thats what I always thought they were. I know the grid lines embedded in roads is something to do with detecting waiting traffic and the thing on the top was the sensor

[Planner1]

The small boxes on top of traffic signals are microwave vehicle detectors. Effectively radar. These are usually backed up by a buried inductive loop vehicle detector (essentialy a loop of cable buried in a slot in the carriageway) set just back from the stop-line. This is the modern replacement for the older system which comprised a series of 3 (more on faster roads) inductive loops buried in the carriegeway at set distances back from the stop - line.

 

The buried detector loop at the stop line is essentially a back-up as the microwave detector is a dynamic detector which only picks up movement above a certain speed. The buired loop detects the presence of a vehicle / cycle.

 

They pick up moving vehicles and tell the signal controller that there is a demand to run that approach. When the green light is on that approach they can extend the amount of green time. (signals generally have set minimum green time and maximum green times, however many sets of signals on main roads operate under Urban Traffic Control computer control for at least part of the day, so they work in a fairly fixed sequence.)

 

When traffic signal detectors fail, they fail "safe". ie they place a permanent demand for that particular approach. This is why on some junctions (like Gleadless / Blackstock), the signals will run to the side road when there is no traffic on it. Sometimes the buried detectors fail and can't be replaced because the carriageway is in such a state. There's also the matter of economics, it can cost a lot of money to replace some of the buried loops and there are over 400 sets of signals in Sheffield. There's often not enough money in the budget to deal with all but he most urgent ones.

 

So, flashing your lights at traffic signals will not make anything happen!

[PeteC]

Well just do what i do.. don't jump read lights and don't speed! afterall as a load of people found out on the A66 the other day - you never know when there may be a mobile camera about.. and it was 3am!

 

Not that anyone i see on the roads gives a ****e about traffic lights anyway - bloody 44tonne low loader pulled out at the lights at university while they were on red - all i heard was 3 crashes as the traffic hit him last week

[sidewinder]

Anyone know what the penalty is for running a red light? (whilst NOT speeding)

[never wrong]

Anyone know what the penalty is for running a red light? (whilst NOT speeding)

 

£60 fixed penalty 3 points