Michelle McPherson: Rail trail’s despised ‘glassphalt’ surface doesn’t deserve its bad rap

Wednesday, April 09, 2014
AMHERST — The Norwottuck Rail Trail Rehabilitation Project now underway includes a range of updates for the bike bath that extends from Damon Road in Northampton to Station Road in South Amherst. The project is good news for many bicyclists who use, and who are afraid to use, the popular bike path that extends from Easthampton to Belchertown. Most of the bike path is now paved with glass containing asphalt (often referred to as “glassphalt”).

Glass shards gradually emerging from this pavement are notorious for puncturing bicycle tires, posing health and financial risks for the path’s users. The rehabilitation project, which started last June and is scheduled for completion this August, involves repaving the path to eliminate the ground glass fragments, widening it from 8 feet to 10 feet where possible, re-surfacing the path’s four bridges, upgrading road crossings and improving its parking lots.

Since the path’s first pavement was laid almost 20 years ago, many Valley residents have given up on glassphalt. When it first came into use in the 1960s, it was hailed for its beauty and for its recycling of crushed glass bottles which, because of their mixed colors, could not be sold for reuse in glassware manufacturing.

By the time the Norwottuck Rail Trail Advisory Committee first decided to employ it, glassphalt had been used successfully in several high and low traffic areas, including New York City’s 5th Avenue and several places in Baltimore. It was known that glass fragments lying parallel to the surface of the glassphalt, if large enough, could marginally reduce the pavement’s skid resistance, so glassphalt could not be used on highways, and required glass fragments that had been crushed to a sufficiently small size.

For all the heavy traffic it supported, glassphalt never posed a threat to tires. Where the broken or waste glass known as cullet was plentiful, typically near large glass recycling facilities, glassphalt use was often slightly cheaper than traditional asphalt, and helped local governments save on municipal glassphalt processing costs.

The advisory committee, happy to create an eco-friendly and economically sound bike path, had the 11 miles paved in glassphalt.

Several tons of waste glass were redirected from local recycling facilities — but with unfortunate results. Bikers occasionally reported tires tearing open, especially in the rain. It turns out that the contractor responsible for making the glassphalt failed to heat the glass to the recommended 1,800 degrees Fahrenheit, which would have melted all sharp edges well enough to eliminate risks of punctured tires.

For 20 years, bikers have cautiously endured or avoided the Norwottuck trail, and now the committee is working to repave it.

With what? Regular asphalt, of course. It is now commonly understood that bikes should not travel on broken glass. But this understanding is flawed: there are in fact proven ways to make glassphalt safe for bike travel.

The failure of the last paving was not in the use of glassphalt, but in the mishandling of the cullet.

This oversight would be quite simple to correct, giving the bike path travelers a safe pavement to use and continuing our Valley’s tradition of making eco-friendly choices as a community.

Michelle McPherson is a fourth-year student at Amherst College from Queens, N.Y.