Dynamic Signs – Edited, and with thanks, from the Journal of Consumer Research

Researchers from the University of Michigan and Brigham Young University (BYU) have discovered a way to provide a little extra safety margin when it comes to near-accidents. They have found that people react significantly faster to warning signs that depict greater movement.

‘A sign that evokes more perceived movement increases the observer’s perception of risk, which in turn brings about earlier attention and earlier stopping,’ said Ryan Elder, a professor in BYU’s Marriott School of Management, and co-author of the study. ‘If you want to grab attention, you need signs that are more dynamic.’

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Dynamic signs are those that include images appearing to move at a higher speed. For example the cross- walk sign from the US, left above, with the figures apparently showing little speed of movement, has very little dynamism. The sign in the middle, from Poland, with people running, has more, and the one on the right is highly dynamic – the figures appear to be sprinting.

‘If the figures look [as if] they’re walking, then your brain doesn’t worry about them shooting out into the road,’ Elder said, ‘But if they’re running, then you can imagine them being in front of your car in a hurry.’

In one simulator experiment, researchers found that drivers reacted an average of 50 milliseconds faster to warning signs with higher dynamism. For a car going at 60 mph, that 50 milliseconds translated into an extra 4.4 feet travelled – which could make a difference in close shaves.

Advance Warning of Speed Limits

Thanks to Group member Doug Barr for his piece commending ‘slow-down zones’ with progressively reducing speed limits before a town or village 30 mph limit. Doug also floated the idea of different speed limits on each side of the road in areas like this.

For example, coming into Macclesfield from the north on the Silk Road, there is a 30 mph limit to protect the pedestrian crossing just before the Hibel Road roundabout. This is very sensible, even though the limit is commonly more honoured in the breach than in the observance. Leaving the roundabout northwards, however, especially as the road is a dual carriageway, maintaining the 30 mph limit for the southbound protection distance before you reach the national limit signs often causes visible frustration among, and unpleasant tailgating from, following drivers. In the early days of the IAM, this would have been classed as ‘driving without due consideration for other road users.’ An immediate release to the national limit after the pedestrian crossing would make complete sense.

Doug reported that some people whom he had discussed slow-down zones with had expressed the view that an aware driver should never be caught out by a change from the national speed limit to 30, but others had agreed that slow-down zones were a good idea.

On the A55 westbound (approaching Colwyn Bay?) there used to be, and perhaps still is, a 50 mph speed limit introduced on a curve, down from the national limit of 70 mph, without prior warning. One could be driving at 70 safely and realistically with regard to the traffic conditions, and able to stop within the distance that one could see to be clear, but still be embarrassed to slow down sufficiently and in good time for the 50 limit because of the risk of following traffic being caught napping. This is another situation where distance-to-go signs, like those used before the 30 limit for some villages, but earlier to suit motorway speeds, would be valuable.

For a further thought, here is an item that we first published in our May 2007 Newsletter:


Some towns and villages in Portugal have a sign saying (in Portuguese) ‘Controlled speed’. A hundred metres or so along the road is a set of traffic lights. If a vehicle enters the speed-limited area above the 50 kph speed limit, the lights go red for a short while.

How simple, and how effective. Whether a driver is over the speed limit deliberately or inadvertently, he is brought in check. If he was ‘pressing on’, he will lose more time stopped at the red than he would have done complying with the speed limit in the first place. And the system has the very beneficial side- effect of encouraging a community interest in observing the limits, because if one driver triggers a red, everyone who was observing the limit has to slow down or stop as well.

It would be good to see the IAM Motoring Trust promoting this system in this country. It would not bring in the revenue stream that ‘gotcha’ cameras 50 yards or so inside speed limit signs probably do, but as a positive measure inviting the intelligent and public-spirited cooperation of all the driving and riding community, it would be excellent.

Snake-bite, why Towcar-trailer weight ratios matter

The caravan clubs recommend that the Maximum Technically Permitted Laden Mass (MTPLM) of a caravan should not exceed 85% of the kerbside mass of the towcar. Here is an example of the reason why:

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This classic Rolls-Royce Silver Shadow had just been collected by its new owner. He was transporting it on a trailer to Spain for a classic car rally. He was towing it behind a Toyota RAV 4 with a kerb weight, depending on model, of between 1.5 and 1.7 tonnes. The weight of the Silver Shadow would be about 2.1 tonnes, giving a weight ratio of around 125%, before taking account of the trailer on which it was being carried.

Within a few miles of the driver setting off, the trailer began to snake, and it eventually threw the Rolls- Royce off. The A350 near Stoney Gutter, Wiltshire, was closed for more than three hours while the debris was cleared. To make matters worse, the owner later discovered that the Rolls Royce’s insurance did not come into effect until midnight on the day of the accident, so that he cannot recoup the cost of the damage.

Count Down Speed Limits – Doug Barr

I was recently working in Llanelli, and rather than take the obvious M4–A449–A40–M50–M5–M6 route back to Congleton I used the A483 instead. This route isn’t any quicker, as it also takes just over 4 hours, but it is only about 170 miles rather than 220 and the scenery is more interesting.

Something which I noticed and which seemed like a good idea was that before the road passed through villages and towns there would be a couple of hundred yards of 50 mph limit, followed by a couple of hundred yards of 40 mph limit, before the 30 limit for the village or town. As the road wasn’t exactly straight it wasn’t possible to see a village half a mile ahead and slow down in advance. It seems that rather than having a situation where you come round a bend to be faced with a 30, and rather than start the 30 limit before it is needed, the traffic engineers have decided to indicate that there will be a lower limit coming up and give the road user time to adapt their speed.

The result as far as I could see was that rather than braking for a change from the national speed limit (NSL) to 30, it was possible to comply with the limits simply by easing off on the accelerator. The result was a smoother drive, less wear and tear on the brakes, and a better fuel consumption.

I didn’t notice any speed cameras in these ‘slow down zones,’ so I am happy to believe that these areas are genuinely there to improve safe traffic flow rather than to raise money. Some people that I have mentioned this to disagree and think that an aware driver should never be caught out by a change from the NSL to 30, but others have also thought that this is a good idea.

Now, to be controversial, how about having different speed limits on each side of the road? The NSL–50– 40–30 arrangement works when entering a village or town, but there is no reason why on leaving the village the speed limit shouldn’t go straight from 30 to the NSL.