- Low speeds. Vehicles must have a low speed (between 15 and 20 mph) and yield to traffic before entering a roundabout. Fewer collisions occur and they are usually minor due to the low speeds.
- One-way traffic. Roads entering a roundabout are slightly curved to direct drivers into the intersection helping them drive counterclockwise around the circle. The curved roads and one-way travel around the roundabout exclude the possibility for T-bone and head-on collisions.
- No green light to catch. Roundabouts are intended to ensure a continuous, circular flow of traffic. Because of this, drivers don’t have a reason to speed up to try and “catch the green light”, like they might at a light controlled intersection.
- Pedestrian safety. Using the median (splitter) island allows you to cross one direction of traffic at a time.
- Reduce delay, improve traffic flow. Vehicles don’t have to fully stop , only yield, so the junction can handle greater volumes of traffic. Roundabouts are also useful when drivers miss their turns, as they can proceed around the circle until they find the right direction.
- Non-stop working: Roundabouts are also more effective during power outages. Unlike traditional signalized intersections, which must be treated as a four-way stop or require police to direct traffic, roundabouts continue to work as usual.
- Reduced long-term operational costs. Roundabouts have no electrical costs, no hardware and lower maintenance costs. In addition, the service life of a roundabout is twice longer than the service life for traffic signals.
- Less space needed. Roundabouts usually require more space for the circle itself but saves much more area because they require less canalization lanes around the intersection.
- More environmentally-friendly due to less vehicle emissions, fuel use and noise.
Many vehicles must wait for the light to turn green in a signalized intersection. While stopped, the vehicle’s exhaust emits more undesirable pollutants and gases into the atmosphere. Because roundabouts often eliminate such stops and improve traffic flow, they also reduce vehicle emissions and fuel consumption.
- Enhanced aesthetics by landscaping. There are many examples of how roundabouts can improve roadways perception with grass and plants or even using sculptures and small monuments.
Roundabouts are not the traffic design solution for every situation. There many variables to keep in mind when designing an intersection, but usually a roundabout is not going to be efficient or safe in the following situations:
- Minor streets intersections in residential areas, due to a low speed traffic
- Where a satisfactory geometric design cannot be provided.
- Where a signal interconnect system would provide a better level of service.
- Where it is desirable to be able to modify traffic via signal timings.
- Where a roundabout would be close to existing signals and queuing from the signal could be a problem.
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