The right priorities

How traffic can be made safer and smoother — if you’re not bumping up against status quo bias

Until we are all moving about in autonomous vehicles, we have to do the hard work of driving ourselves. And when I say hard work, I am not being sarcastic. Operating the pedals and the steering wheel in a car may not require much physical effort, but the cognitive load of getting to our destination without hitting other road users and obeying the rules is significant.

One such situation where there is plenty of scope for collisions is at road intersections. I grew up in Belgium which, like its neighbouring countries, operates a general rule stipulating that traffic coming from the right takes priority. The origins and justification of the rule are unclear, but it was apparently first introduced by a Parisian police commissioner in 1910 (although it was only adopted in Belgium in 1961).

At first sight, the rule seems simple enough: most people know their left from their right side, and so there should be no confusion whether to give way, or whether to enjoy one’s priority.

Unfortunately, reality can be a bit more complicated. It doesn’t take much imagination to understand the chaos that would ensue if the rule applied to major roads with heavy traffic, which would need to give way to all vehicles coming out of every single side street to its right. Similar trouble would arise at roundabouts (which run anticlockwise in continental Europe) with vehicles already on it needing to give way to traffic about to join.

So, exceptions are necessary. A special traffic sign is used on major roads, indicating (among others) permanent priority over all side roads until revoked. On roundabouts, a specific rule overrides the general priority rule, giving priority to traffic that is already on the roundabout. And for countless other junctions where the general rule is, for one reason or another, not applicable, another traffic sign is used to override it just for the next junction.

Look ma, no traffic signs, and no priority rule!

For more than two decades, I rode bicycles and drove a succession of cars in this environment, which gradually became as normal and comfortable to me as water to a goldfish in a bowl. To me, this was the natural way, nay the only way, to ensure smooth and safe traffic at intersections. Until I moved to the UK — where there is no overriding priority rule.

How on earth do they avoid utter mayhem at every junction? To my surprise, apart from a very occasional octagonal STOP sign, there were no traffic signs relating to the priorities. None. What I did notice immediately, though, were the road markings: white lines clearly indicated who needs to give way to whom — at pretty much every single junction.

But what struck me the most, as I began to clock up the miles in my new country, was the fact that I rarely had to look at the lines to know whether I had priority, or whether I needed to give way. It seemed entirely natural.

This is, I now realize, why it is such a successful approach. Drivers who, at every junction, need to work out which rule applies, and search for signs that might overrule it, inevitably divert attention away from the road, and of course they may miss a vital road sign. This is making it difficult to do the right thing — the exact opposite of the first principle of good behavioural design: make doing the right thing easy.

Sometimes this does mean making the wrong thing harder. Most of us will be familiar with traffic calming measures like speed bumps and chicanes with plant containers that actually force us to reduce our speed if we don’t want to damage our car: they make speeding more difficult. At hazardous junctions, the road layout is sometimes changed with the addition of a roundabout and curves in the road, to slow down the traffic. And sometimes the interventions are entirely visual, using fake 3D road markings or simply lines to trick drivers.

Fake speedbumps, real effect. (photo via iNudgeyou)

But the way priorities are managed at junctions in the UK shows that sometimes very little is needed to reinforce what is already hinted at by the environment. If a road feels like a main road, then it is given priority, and if it is not, then it is made to give way to the main road.

In countries where the ‘priority to the right’ rule prevails, many collisions happen at junctions where the general rule is in conflict with the environmental cues. On a straight, wide road, you do not expect to have to give way to traffic coming out of a small side street, yet — unless a sign tells you otherwise, that is exactly what you have to do.

On November 10th, 2017, the small Flemish town of Glabbeek abolished the rule on its local roads. Nearly 85% of the population had supported the idea in a poll, and the council decided to put their citizens’ wishes into practice. Just two junctions needed adjustment, and in all other situations, a system of main and side roads was the easy, logical choice. Did it work?

Mayor Peter Reekmans thinks so: “It is one of the best decisions the town council ever took to improve traffic safety, as there is now no longer any doubt that smaller side streets need to give way to main roads.” And the figures seem to confirm that aligning priorities with the actual situation was a good idea. The number of collisions due to violation of the priority rules dropped from 18 per year to just 3, and the number of speeding offences fell by 30%, with a similar reduction in the offenders’ actual maximum speed.

Not surprising then that the VAB, one of the largest motorists’ organizations in Flanders, is now advocating scrapping the priority to the right rule nationwide. Spokesman Maarten Matienko believes it will lead to a similar reduction in the 15,000 accidents each year, which result from drivers who do not obey the rule: “there should be no doubt who needs to give way at a junction.”

Begone, priority to the right! Your mayor commands you! (image via

But the proposal got the cold shoulder from Flemish Mobility Minister, Ben Weyts. It would be too expensive to place hundreds of thousands of new traffic signs, and we need to hang on to it as a fall-back solution, in case the signs are damaged, and people are confused again. This is because, according to the Belgian highway code, making a road a main road requires road signs — as many as four at every intersection (two on the main road, and one on each side street). You can see his point.

It nevertheless looks like a bad case of status quo bias. The minister could have taken a very different approach. He could have looked at the potential benefits of the suggested measure. How many of the 15,000 collisions annually would need to be prevented to justify the installation of new signs? Perhaps even more radical, he could have considered how priorities are managed at junctions in the UK, and learn how safe and smooth traffic can be achieved without signs. He could have proposed a change in the traffic code, and rely on road markings to reinforce what, in most places, already feels natural as a result of the road architecture.

15,000 accidents each year (that is in for every 200 households) strongly suggest that the ‘priority to the right’ rule, more than 50 years after its introduction, has not been able to override the cues drivers receive from the road layout.

Here is an opportunity to make traffic safer, based on evidence from a small town and a large country. Sadly, it is an opportunity that is not a priority.

Originally published at on March 29, 2019.

Thanks for reading this article — if you enjoyed it, please share it far and wide. (There are Twitter and Facebook buttons, click here to post it on LinkedIn, or simply copy and paste this link.) And in case you want to read more articles like this one, see all my other posts (I publish one every week) here. Thanks!

Accidental behavioural economist in search of wisdom. Uses insights from (behavioural) economics in organization development. On Twitter as @koenfucius

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