Smoothly in Roundabouts

One of the most famous ones goes around the Arc de Triomphe in Paris: Roundabouts make the traffic safer and lead to a free flow. They exist in different dimensions and in various designs. 

The Arc de Triomphe has up to eight lanes – it depends on the volume of traffic. Photo: Fotolia – A.G. photographe

Roundabouts are about as French as baguettes and good cheese, with between 30,000 and 50,000 “rond-points” scattered across the country, far more than in the USA or Germany. There is plenty in their favor. “Roundabouts are a safer alternative to traffic lights and stop signs,” asserts the renowned US organization Insurance Institute for Highway Safety (IIHS). Often undervalued by many of the public, roundabouts force drivers to reduce and control their speed upon entering and negotiating the intersection. Stamping on the gas pedal on amber to make it through is not an option on a roundabout.

Roundabouts reduce the risk of accident

Serious accidents upon turning left or right are virtually precluded, as are head-on collisions. A city roundabout can reduce the risk of accident by more than 40 percent, as French accident researchers discovered. “The slower speeds and reduced points of conflict cater for very high traffic safety, when compared with other intersection formats,” maintain the UDV (Insurers’ Accident Research) in Germany. Depending on the volume of traffic, roundabouts are also often more effective than intersections with traffic lights.

The phasing of a set of traffic lights at conventional intersections in bigger cities must be laboriously coordinated with that of others, as well as the traffic volume at that time of day. There is no avoiding a wait – the “green wave” remains the stuff of legend. Roundabouts, on the other hand, improve traffic flow, as they adapt like a living organism. When there is little traffic, nobody must wait, whereas under heavy loads, the vehicles move slower while remaining in motion. This isn’t just more agreeable for drivers, it also benefits the environment. The reduction in stops and starts reduces both fuel consumption and emissions.

By converting conventional crossroads – with their safety issues – into roundabouts, “an outstanding improvement in traffic safety can be realized,” underlines the UDV. Mini-roundabouts with an external diameter of between 13 and 22 meters can be more easily integrated into small towns and villages than small roundabouts, which feature a diameter of between 26 and 35 meters. Mini-roundabouts too are very safe, and have a relatively high capacity of up to 18,000 vehicles per day. Often, they can be installed with very little reconstruction of surrounding infrastructure, and even made so that larger vehicles such as buses can drive directly over them. The islands of small roundabouts are however a no-go for vehicles. They are designed for higher traffic loads of up to 25,000 cars per day.

Multilane roundabouts should be operated by means of traffic lights

Large roundabouts with a diameter of over 40 meters direct multiple lanes of traffic next to one another, and are suitable for main thoroughfares with more than 30,000 vehicles per day. According to the UDV experts, these should be operated in conjunction with traffic lights. A special form of the large roundabout is the so-called turbo-roundabout, with an even higher level of effectiveness. Even prior to the roundabout entry, vehicles are presorted according to their intended direction.

Roundabouts have, quite simply, less points of conflict than conventional junctions. Safety is however less pronounced on roundabouts of two or more lanes. Cyclists in particular need to be especially careful here, experts from France insist. The most important rule is not to hug the right-hand side of the lane, rather ride in the middle of the lane to ensure good visibility and to demand the attention of other road users. Riding too far over to the right creates the risk of being overtaken and being cut off at exits.

The Placa d’Espanya is one of the most famous places in Barcelona. Around the fountain in the center of the place, there is a roundabout with six lanes. Photo: Fotolia – marcorubino

It is important that roundabouts are clearly signposted and marked, even at night. If there is a traffic island, this can be edged with a border of just a few centimeters. Pedestrian crossings must also be clearly marked. Roundabouts are also a safety win for pedestrians – the weakest of road users – as the traffic flows in just one direction, and the distance to be crossed is relatively short.

The most beautiful roundabouts are awarded every year

Despite all of this, there are still risks. Entering the roundabout at excessive speed can result in a harsh landing onto the central traffic island. In Germany, this is a perennial source of discussion, with authorities making constant demands to redesign and remove possibly hazardous obstacles. Internationally, however, this genre of complaint is a rarity, and a range of installations can be found on the world’s roundabout islands. There is even an annual award for the world’s best roundabout idea – the “International Roundabout of the Year” – which is conferred by the UK’s Roundabout Appreciation Society.

Roundabout safety could be further improved if European countries could agree upon a uniform set of rules. Travelling between countries is currently prefaced with research into the intricacies of destination countries’ conventions when it comes to roundabout usage. But these are not always clear-cut. Throughout France, vehicles already negotiating the roundabout have right of way, however, there is one exception. On the Arc de Triomphe, these road users must brake, allowing new arrivals to enter the roundabout.