BOULDER, Colo. -- Someone is suggesting that Boulder County residents stand up for their right to drive by disrupting a bike race next month.

An anonymous flier being circulated in mountain neighborhoods asks residents to drive slowly on the return route of the Sunrise Century. It suggests that they block riders by pretending to be broken down. Click to see the flier.

It began appearing last week, a few days after a driver suspected of endangering a cyclist was given a ticket.

Boulder County sheriff Joe Pelle doesn't think the effort has much support. But he has increased patrols in the area in recent weeks and the Colorado State Patrol advised against interfering. Trooper David Hall warned that drivers ought to think twice before trying to block the riders.

"We would highly discourage people from engaging in that behavior," Hall told the Daily Camera. "It’s illegal. You can’t block the path of events or traffic."

There's been tension between bikes and cars for years but Pelle said things have been getting worse in advance of a new state law giving greater protection to bikes. It takes effect Aug. 5.