Ayres Knowledge Center Using Bike Boxes to Increase Visibility and Safety | Page 10

DON’T COLOR APPLICATIONS MAKE
PAVEMENT SLIPPERY?
Typically bike boxes are colored using paint, acrylic resin, or
thermoplastic . To ensure the stopping distances and drag
factors are appropriate as mentioned before, pavement
locations where the bike boxes are placed must be cleaned
of all grit and dirt before the application process begins.
The product used typically contains some sort of primer,
resin, powder hardener, and/or aggregates to help create
an anti-skid, frictioned surface that helps motor vehicles
and bicyclists not to skid when coming to a stop.
The Portland study attempted to look at whether color
pavement treatments increased stopping distance:
“We dragged a drag sled (consisting of a 20.75-pound
section of concrete-filled, rubber car tire attached to a
hanging weight scale) parallel across the surface being
measured in the direction of traffic flow. … A drag factor
was calculated by taking the average of five recordings at
each location and dividing by the weight of the sled. Drag
factors were calculated at a variety of locations, including
on the green thermoplastic surface (both on sections that
appeared to be worn and unworn), on white stop bars and
lane stripes, and on adjacent asphalt.”
10 | USING BIKE BOXES
The differences observed were insignificant. “The green
surface had an average drag, across all locations, of 0.75.
Excepting a noticeably worn (and grey) section of the
green t