ASPHALTopcs | Summer 2017 | VOL 30 | NO 2

TECHNICALLY
SPEAKING
by Vince Aurilio
Executive Director, OAPC
Intersections: Approach with caution
of a racetrack or a runway). In fact,
slow-moving heavy vehicles at an
intersection actually put more stress
on pavements than those moving
faster.
RR20 Lundy’s lane at Drummond Road, City of Niagara Falls,
rehabilitated in 2011/2012. (Niagara Region)
The same traffic conditions that add to the stress
of driving at intersections (about 30 per cent of
fatalities occur at intersections) 1 also add to the stress
on pavements. Whether you are a driver or pavement
engineer, you should approach intersections with care.
Urban traffic conditions have brought the challenge
of designing pavement for intersections to the top of
the agenda for municipal engineers. The heavy traffic,
braking, accelerating and turning that contribute to the
wear and tear on asphalt are becoming increasingly
severe. Traffic is getting more congested, tire pressures
are increasing, and trucks and buses are heavier.
It is not just the volume of traffic that should be of
concern. Intuitively, most people associate the speed
of the vehicle with the stress on the pavement (think
Engineers need to pay particular
attention to design and material
selection to ensure that the asphalt
pavement at intersections provides
the same outstanding performance
and life-cycle cost benefits as it
does elsewhere.
Rutting is probably the most common indication
of pavement failure at an intersection and can be
the result of inadequacy of the pavement structure,
poor consolidation (compaction), and/or plastic flow
(permanent deformation). The Asphalt Institute in
the U.S. has developed a basic strength approach
to designing pavements at intersections that
addresses all three failure mechanisms:
1. Ensure structural adequacy.
2. Select and control materials.
3. Follow proper construction practices.
As you would expect, aggregates play a very important
role in all three steps.
The most common failure mechanism at intersections
is plastic flow (rutting), and material selection is key in
34 OAPC | ASPHALTOPICS