The death of a cyclist in the Trek Across Maine fundraiser earlier this month has focused attention on the risks that bicyclists face from the draft created by passing vehicles, especially large trucks.

Police say David Leclair, 23 of Waltham, Mass., was probably knocked off balance by the air turbulence from a passing tractor-trailer. They say he died either when he hit his head on the truck or after his arm hit the truck and he was thrown onto the road.

“It would be very difficult to be a cyclist and not have something like this operate as a wake-up call, just in terms of vulnerability out there on the road,” said Brian Allenby, spokesman for the Bicycle Coalition of Maine. “It also throws into focus the need to be hyper-vigilant and aware of surroundings and really riding defensively.”

The Maine State Police’s preliminary investigation concluded that the possible cause of the June 14 crash was the draft created by the truck, which caused Leclair to move to his left, hitting the rear tires of the truck.

That assessment is consistent with what troopers said was a possible contributing factor, and state police Lt. Walter Grzyb said Thursday that nothing in the subsequent investigation has changed that theory.

Police also learned that Leclair was taking a drink from his water bottle and had only one hand on the handlebar, which made him less steady.

The power of the “drag” created by a passing truck — the force of the wind as air is pushed away from the front of the truck and then fills in behind the rig as it passes — is familiar to many cyclists.

“It’s something I personally have experienced many times as well as every other cyclist I know who’s ridden on the road,” Allenby said. “The trucks don’t even have to be doing 50 or 60 mph, they could be going 30 to 40 mph. Any time you’re moving a mass that large through the air, you’re creating quite a bit of turbulence.”

Police have said that Leclair was riding about 2 feet inside the breakdown lane, based on witness statements. The truck was about 2 feet into the travel lane, leaving about 4 feet between the two as the truck passed.

The law requires motorists passing cyclists to stay at least 3 feet away.

Grzyb said the investigating trooper is still interviewing witnesses and hopes to have a final investigative report finished in another two weeks, although it may take longer.

The Trek Across Maine is an annual fundraiser in which more than 2,000 cyclists ride over three days from Sunday River ski resort in Newry to Belfast to raise money for the American Lung Association.

Leclair, part of the athenahealth cycling team from Massachusetts, was killed when he crashed on Route 2 in Hanover just a few miles from the ride’s starting point.

The crash report completed by Trooper Ronald Turnick on the day of the crash was approved by Trooper Kyle Tilsley on Tuesday.

The report indicates that Leclair was riding east, “near the breakdown lane.” The tractor-trailer driven by Michel Masse-Dufresne, 24, of Quebec, also was headed east.

Masse-Dufresne was apparently unaware that the rear of his 80,000-pound truck, which was hauling corn, had collided with Leclair. Masse-Dufresne continued driving until he was pulled over about five miles away in Rumford.

The report says it appeared that Leclair died of neck injuries; however, an autopsy determined the actual cause was blunt trauma to the head.

The crash report notes the road conditions that morning were dry and clear, the road straight and that Masse-Dufresne was not distracted.

A diagram of the crash scene shows there were a series of road signs as the truck approached the stretch of road where Leclair was riding. One indicated the speed limit was dropping to 40 mph, the next said to watch for pedestrians and the third indicated the speed limit had dropped from 55 mph to 40 mph.

The Bicycle Coalition of Maine, a nonprofit group that advocates on behalf of cyclists, says in its literature that motorists should imagine a yardstick poking out the passenger window to gauge 3 feet, the minimum distance a car should be from a cyclist it is passing. Allenby said that is an absolute minimum.

“The example I always give is if a child is standing on the side of the road, would you pass them at 40 mph only 3 feet away? Of course not.”

New Hampshire state law requires a distance of 3 feet between a cyclist and motorist when the vehicle is traveling 30 mph, 4 feet when it’s going 40 and 5 feet when it’s going 50, he said.

In parts of Europe and Japan, where there are many more bicycles and motorized scooters sharing the road with trucks, many trucks are required to have underride side guards. The devices, barriers that stretch between the wheels of the trailer and below the container, prevent cars, cyclists and pedestrians from going beneath a trailer and being hit by the rear wheels.

Certain types of side guards reduce aerodynamic drag, according to a study by the National Research Council Canada’s Centre for Surface Transportation Technology.

However, the 2010 study did not explore the impact of reducing turbulence on safety, or identify turbulence as a significant safety threat.

There are important steps cyclists should take to keep themselves safe, Allenby said.

“One of the biggest keys, especially in urban areas, is to ride in a manner that you don’t surprise … motorists,” he said. “The more you can do to let them anticipate your next action, the safer you both will be.”

When large trucks are approaching, cyclists should grab the handlebars firmly, but not tense up their arms and shoulders, he said.

“You certainly want to have a good grip, but if your arms and shoulders are locked, it’s hard to react,” Allenby said.

That technique, along with other strategies for safe riding in traffic, are taught in many cycling classes, he said. Such classes can be valuable, especially for adults who rode as children and take up the sport again later in life but are now using the bicycle in a much different way, he said.

More information is available on the group’s website at: http://www.bikemaine.org

David Hench can be contacted at 791-6327 or at:

[email protected]