Slow Down

A friend sent an email to the Highways Agency complaining about the variable spped signs on the M1, and that they were almost INvariably slowing down the traffic. The following is their response, and my comments are after!

Thank you for your e-mail to the Highways Agency Information Line today and thank you for taking the time to comment on our Variable Message Signs (VMS). The Highways Agency values the feedback we receive from the travelling public as this is our primary source of identifying how effective our signs are at keeping drivers informed.

On the busiest parts of the motorway network, VMS are set using an automated system called MIDAS (Motorway Incident Detection and Automatic Signalling). MIDAS uses sensors in the road to detect incidents or congestion and then automatically sets advisory reduced speeds (e.g. 60, 50, 40 mph) and warning messages (e.g. Queue Caution) on VMS.

MIDAS has a number of functions, principally safety related with queue protection being one such example. The system provides advance warning to drivers of the formation of queues on motorways, warning drivers who are approaching the back of queuing traffic. Sensors in the road surface detect slowing traffic speeds and electronic signs advise drivers to reduce speeds as they approach the scene. These messages remain until the traffic flow returns to normal and it can appear that the message is incorrect because there is no queuing traffic when you arrive at the scene.

There is also a secondary benefit to reducing the speed of vehicles approaching queuing traffic. Reducing the volume of traffic in an area of congestion means the congestion clears quicker. The result is that the traffic approaching the area where the congestion was will no longer be delayed in their journey by the congestion.

During changing traffic conditions (such as when congestion is dissipating or an incident is being cleared) there is a time lag between traffic returning to normal flows and MIDAS switching off. This is designed to prevent MIDAS switching on and off at regular intervals in stop/start conditions. In addition, MIDAS often detects slow moving vehicles (usually heavy goods vehicles on hills) and advisory speed limits are set automatically, although this may not be obvious to other motorists.

Should you have any further questions about the above issue(s) or any other Highways Agency related issue(s) please do not hesitate to contact us again via e-mail or telephone us on 0845 7 50 40 30.

So, do I think that I might have some comments. Apart from struggling to believe the MIDAS system even exists, how unsuitable is traffic flow to try and automate!

I love the fact that MIDAS will switch off once the flow returns to normal. But the flow can't return to normal if MIDAAS is on because it is telling us to go slowly. The only way flow can return to normal is for us all to think f**k this for a game of soldiers and start going faster than the signs tell us.

They even recognise that to ease congestion you need to reduce the volume of traffic. So how does slowing us all down, meaning that we spend longer in the zone, actually do that. Cars are approaching the zone at 70mph. Therefore the feed in is fast, but the flow through is slow. If I turn on taps and the water coming in is faster than that going out of the plug do you think my bath might overflow. Doesn't take a great mind to see a fault in their logic.

If feedback from the pblic is the primary source for them to identify how effective their signs are, do you think that they will now have identified that they are completely ineffective.!