How Do Portable Traffic Signals Actually Work?

People who are involved in courier work for a living drive a lot, and no doubt have certain things on the road that drive them crazy, such as Portable Traffic Signals (PTS). Here’s our quick reference article on PTS. After you have read it hopefully you will look at them differently.

Temporary Traffic Management

Portable Traffic Signals are all about managing the traffic on a temporary basis, something that all those courier workers who rely on the road for their livelihoods feel very strongly about. While these signals are cheap to hire for local councils and can be a cost effective way to control traffic, they can test the patience of regular road users.

How Do They Work?

For the geeky courier worker, this is where we get technical. The PTS can work in 2,3, or 4 phases, and they function in one of 3 ways, Vehicle Actuated (VA), Fixed Time (FT) or Manually (MAN). Normally the VA mode is used, because of its efficiency. The FT and MAN modes need permission if they are to be used, and the MAN mode must be in place if the traffic is moving at 10mph in a convoy flow situation.

Did you known that the heads of the PTS have integral detectors that work on microwaves? These are set to pick up vehicles approaching at a distance of between 5m and 40m and at speeds higher than 10mph. The signals have what is referred to as a ‘nudge’ circuit fitted that ensures that the signals run on a 2.5-minute cycle.

When you approach in your vehicle, the detector picks up your presence and sends a signal to the control box. As long as there is no other demand from any other direction, the signal turns green for you. You may have noticed that PTS always show a red light when you approach. This is same for all directions. They are waiting for stimulation from an approaching vehicle that will then initiate the control box to permit a green light on only one approach and for a 7 second minimum time. The light stays green until the maximum green time has elapsed or no more vehicles are approaching, or indeed if there is demand from a vehicle from another direction.

How Do The PTS Communicate?

Normally the PTS system is connected wirelessly. The distance between the signal heads has to be carefully measured and should not be greater than 300m. This is so that the time between the red and green cycles is not too long, and traffic flow is kept moving: great news for courier workers. In cases where the distance is over 300m then you’ll see a road worker manually operating the traffic flow.

How Are They Powered?

Mains electricity is often used to power the PTS if they are to be in place for longer than a week, using a supply from nearby street lighting. A generator can be used, although this can be unattractive to local residents because of the noise and pollution. It also requires more monitoring. Alternatively a rechargeable battery is installed. If the PTS are in place for less than 5 days this is a sound option.

So now, as a courier working the roads on a daily basis, you might look at PTS differently. While you sit waiting for the lights to change, think about how they work and marvel at how clever the system is in keeping the traffic flowing and ultimately making your life easier.