Roundabout intersections, a common sight in Europe, the United States and even New Zealand, are gaining attention in Japan as means of cutting costs and emissions, as well as boosting traffic safety and facilitating smooth evacuations during disasters.
Due to the structure of roundabouts, which connect crossing roads via a circular one, vehicles have to reduce speed before entering, resulting in fewer traffic accidents. They are also unaffected by power outages as they lack traffic signals.
However, as drivers are not guided by traffic lights at such intersections, they are left to judge how to navigate them by themselves.
Towacho intersection in Iida, Nagano Prefecture, was converted into a roundabout February 5. It was the nation's first attempt to create a roundabout by removing traffic signals and reshaping the intersection.
A city government official said, "As [all vehicles] reduce speed at the intersection, many residents have said it has become safer."
Roundabouts can also reduce maintenance and electricity costs for traffic lights, which have a service life of about 20 years.
As vehicles do not need to wait for traffic lights to turn green before advancing, the city estimates that carbon dioxide emissions at such intersections can be reduced by about 10 per cent.
Professor Hideki Nakamura of Nagoya University, an expert in infrastructure engineering, recommended roundabouts in rural areas. "In places where traffic volume is low and securing land is easy, [roundabouts] can be effective," he said.
Local governments in areas devastated by the Great East Japan Earthquake are considering roundabouts, as they do not need traffic signals. Amid power outages after the disaster, traffic fell into disarray.
It is estimated that 677 people in the three disaster-hit prefectures died in the quake-triggered tsunami because they were unable to evacuate by vehicle.
Thirty police officers manning intersections where traffic lights had lost power died or went missing in the disaster.
In Iwate Prefecture, the introduction of a roundabout is being considered at an intersection of prefectural roads in Rikuzen-Takata, which was severely damaged by the tsunami.
Although people are urged to evacuate on foot when a tsunami is approaching, some evacuees need to use vehicles if they are with elderly people or others with reduced mobility.
Residents say they expect more roundabouts in the city would help them evacuate more smoothly.
Roundabouts are also being considered in Tokai and other regions that are expected to be hit by a magnitude-9 Nankai Trough earthquake. The Land, Infrastructure, Transport and Tourism Ministry has held meetings with local governments and police authorities to study their introduction.
While roundabout intersections have many merits, they also have disadvantages.
At conventional intersections, drivers can rely on traffic lights to decide for them whether to stop or go. However, at roundabouts, drivers need to make judgments on their own, in accordance with traffic laws they may not be familiar with.
Some residents of Iida, where a roundabout was recently introduced, expressed concern. "Some drivers don't use blinkers when they merge with other cars in the intersection," one said.
In some cases, drivers have successfully entered the intersection but failed to exit in a timely manner.
Soichi Shimizu, 51, a motoring journalist familiar with road conditions in Japan and abroad, said: "Drivers may not be accustomed to roundabouts at first, but all they basically need to do is make a left to enter and another left to exit. Furthermore, if efforts like reducing the width of the circular road are taken to make drivers less tempted to speed, safety will increase."
Roundabout intersections can control traffic at intersections with five or more crossings. According to the Tokyo-based International Association of Traffic and Safety Sciences, roundabouts became popular in the 1960s in Western countries.
Germany has more than 4000 such intersections, while in France, all intersections in principle in rural cities are roundabouts. Japan has about 10 roundabouts in such cities as Toyota and Hitachi.