ROADBUILDING
STRAIGHT TALK ON PAVING ROUNDABOUTS TRAFFIC FLOW, PROPER MIX, AUTOMATIC GRADE CONTROL ALL TOP TIPS FOR ROUNDABOUT CONSTRUCTION BY LEE TOOP, EDITOR
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popular traffic management approach in Europe for many years, roundabout intersections are becoming a regular sight on North American roads. The safety aspect of roundabouts, which reduce injury crashes and fatalities by a significant amount over traditional signalled intersections, are a big draw for road planners at all levels. Roundabouts, however, are a little more complicated to construct and pave than regular intersections. The flow of traffic on roundabouts can mean different wear and tear on road surfaces, and thus it is important to plan a roundabout paving construction project carefully, use the right asphalt mixes and compact surfaces in a way that ensures longevity.
TRAFFIC FLOW CONSIDERATION CRITICAL FOR ROUNDABOUT PLANNING
Paving crews working on roundabout projects must be aware that everything from traffic movement to construction itself can cause problems with road surfaces, according to Todd Mansell, a paving product application specialist with Caterpillar. “The wheels are turning, the vehicles are putting forces on the pavement – a lot more lateral force or stress strain on that
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asphalt pavement compared to a straight roadway. And, we have a lot of traffic with acceleration, stops and starts along the approaches,” Mansell said. “It can be difficult to perform the paving because of the many joints involved, longitudinal and transverse, and all the approaches.”
PLAN AHEAD FOR ROUNDABOUT CONSTRUCTION
Good pavement relies on a good base, so it’s important that the condition of the road base be considered before paving starts. If rehabilitating an existing roundabout, milling the full surface is highly recommended. For paving a new roundabout, ensure that the aggregate base is protected from damage and grading plans are in place to ensure proper drainage. “Base repairs on a roundabout are more difficult to go back and do afterward, and get everything to match,” Mansell noted. Truck movement should be planned early to reduce strain on the base, and truck drivers should be warned to avoid too many trips onto potentially fragile base courses. The base design also ties in to drainage – the grading plan needs to be precise to ensure water moves in the right direc-
