OHM - Roundabouts

Roundabouts

What is a Modern Roundabout?

A modern roundabout is a transportation management tool that moves traffic through an intersection without the aid of traffic signals. It involves one-way-traffic moving around a circular central island where entering traffic must yield to the traffic already in the roundabout. The objectives of roundabouts are to reduce traffic speeds and reduce the number and severity of crashes, while improving traffic flow. Roundabouts are designed to accommodate all sizes of vehicles.

A Roundabout is Not a Traffic Circle
Many people confuse modern roundabouts with traditional traffic circles or rotaries, such as those found on the East Coast. Three basic principles distinguish the modern roundabout from a traffic circle.

Videos

Safety Benefits of Modern Roundabouts

According to the Insurance Institute for Highway Safety, installing a roundabout typically results in:
76% reduction in injury-accidents

90% reduction in fatalities

40% reduction in pedestrian injuries

75% fewer “conflict points” compared to standard intersections (rollover diagram to the left to enlarge)

Why do roundabouts have such a good safety record?
Conflicts are reduced
With fewer conflict points, roundabouts eliminate the potential for hazardous conflicts, such as right angle and left-turn head on crashes.

Speeds are reduced and are more consistent
Low speeds driven in roundabouts allow drivers more time to react to potential conflicts, thus helping to improve the safety of roundabouts. Since most drivers travel at low speeds (15-25 mph) through roundabouts, crash severity is reduced compared to traditional intersections.

Pedestrian friendly
Pedestrians need only cross one direction of traffic at a time at each roundabout approach, as compared with signalized intersections. The distance the pedestrian travels to cross traffic is also shorter than a traditional intersection.

How to Navigate

Follow these simple rules for driving in roundabouts:
Speed
Slow down! The objective of the roundabout is to keep traffic moving and allow for more capacity. But to do it properly and safely, it must be done at a low speed. Smaller roundabouts limit speeds to 15 mph, while larger roundabouts allow for speeds of 20-25 mph.

Yielding
Always yield to traffic in the roundabout and to your left. Motor vehicles should yield to bicyclists and pedestrians.

Pick your lane
Before entering the roundabout be aware of your intended exit and pick the appropriate lane. Look for the green guide signs and black-on-white lane-use signs as you approach the roundabout. These will provide general directions for roundabout use. The rules are similar to other multi-lane intersections. Make a left-turn from the left-most lane and a right-turn from the right-most lane. For a multi-lane roundabout, the left lane allows for going straight, turning left or making a U-turn. The right lane allows for going straight or making a right turn. When entering and navigating the roundabout, follow the lane lines.

Never pass in the roundabout
Always check your rear view mirrors for vehicles in the outside lane exiting the roundabout. If you cannot move to the outside lane safely to make your exit from the roundabout, simply travel through the roundabout circle again, until there is an opening.

Allow large vehicles the extra turning radius needed to navigate the roundabout properly. Never pass or drive next to a large vehicle in the roundabout.

Walking

Pedestrians have the right of way within crosswalks at any intersections, including roundabouts. For safety’s sake, pedestrians must never walk into the path of a vehicle if it is so close that it is an immediate hazard.

Walk around the perimeter of the roundabout. Do not cross the roadway to the central island.
Use the crosswalks on the legs of the roundabout. Crosswalks are placed one to two car lengths back from the roundabout entrance areas. Approaching cars will yield to enter the roundabout behind the yield line. Pedestrians may cross the roadway behind the car at the yield line.

Look and listen for approaching traffic. Choose a safe time to cross from the curb ramp to the median opening. Although you have the right of way, if approaching vehicles are present, it is best to first satisfy yourself that vehicles have recognized your presence and right to cross. When crossing an entry or exit with more than one lane, be sure that vehicles in adjacent lanes are coming to a complete stop before proceeding. Use the median or “splitter island”. It allows you to cross one direction of traffic at a time.

Bicycles travel through a roundabout one of two ways:

As a pedestrian, traveling on the sidewalk and walking the bike through the crosswalk.
As a vehicle, traveling on a roadway.

Take the lane and circulate as a vehicle, making sure to yield to traffic in the circle when entering.
Ride at the speed of the circular roadway to discourage cars from passing you.
When you exit the roundabout, use your right hand signal.
If you are unsure about using the roundabout, dismount and walk your bike as a pedestrian at the designated crosswalks.

OHM's Roundabouts Services
Studies Modeling Design Construction

Here are a few of our favorite roundabouts:

Baldwin/Indianwood/Coats Roads
Orion Township
The first multi-lane roundabout in Oakland County, this replaced a historically unsafe
Y-shaped intersection