Partial repost with permission from Flatironbike.com. Please go there to read the full article
Two bicyclists have been killed at the intersection of US-36 and Violet Avenue since 2009. The most recent was TJ Doherty, on July 24th, 2012. Both cyclists were headed southeast on US-36, and were hit by cars traveling northwest, making left turns onto Violet. In this area US-36 is just outside of Boulder’s city limits, in the county, but it’s the Colorado Dept. of Transportation (CDOT) that’s responsible for it. Looking at the aerial view below we can explore why this intersection might be particularly dangerous for cyclists.
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Northwest bound vehicles on US-36 have a dedicated left turn lane, and no obligation to stop before making their turn. The angle that Violet Ave. makes with the highway is quite oblique, meaning that it can be taken at high speed, and because US-36 has a speed limit of 55 mph in this area, cars often will take it at high speed if they don’t see any oncoming traffic.