Thursday, May 26, 2011

John Allen: When the Marketing Dept. Plays Traffic Engineer

The product shown in the picture below, small raised barrier lane dividers designed to be installed between bike lanes and regular travel lanes, are critiqued on John Allen's bicycling page. These are marketed as "...a smart, safe solution that provides a visual separation between vehicle and bicycle lanes. ...."

The raised protuberances are marketed as "a smart, safe solution that provides a visual separation between vehicle and bicycle lanes."

But the design seems to add a (not so) hidden hazard.

Keeping cars out of the bike lane in itself is not always a good idea, since in this case the fix also keeps cyclists from merging into traffic to make left turns or for any other reason that requires leaving the bike lane (obstructions, overtaking, etc). It could also force cyclists and motorists into "coffin corner" situations at intersections if applied right to the intersection. It also makes street cleaning difficult. At least for the bike lane.

More seriously, raised features such as these, which are somewhat analogous to shoulder paving lips, could induce diversion falls if hit at a grazing angle. The two sides of the small barriers are advertised as asymmetric, but I'd hate to hit one at a glancing angle nonetheless (did anyone do an experiment?). Striking these at a glancing angle might possibly cause a cyclist to lose steering and balance (in the same way a shoulder lip can do so) and topple over into the travel lane.  John Allen discusses this possibility in his own post, citing MUTCD sources that warn against installing such features.

Anyway, its important to ask the questions in advance. It seems to me that if someone INSISTS on a passive barrier more compelling than a paint stripe along the edge of the bike lane, something like a narrow rumble strip would be preferable. A rumble strip is negative in profile rather than positive and would be aggravating but not dangerous, seemingly far less of a problem. Plus, it would have the same effect--a warning to a distracted motorist, perhaps, that he/she is encroaching on a bike lane. These barriers are certainly not going to stop a car but could have unintended consequences to a cyclist.

With Trinity Drive reconstruction on the table, I'd hate to see something like this suggested by a non-cyclist.


Walter Enomoto said...

Aloha Khal,
Just received word from a traffic engineer here asking us about this same questionable product. We responded with comments similar to yours and John Allens. I've forwarded this info to all other bike advocacy groups in Hawaii and so far the response has been similar also.
For a company with the word "Logix" in their name, they certainly showed that they didn't use any in coming up with this product.....

Khal said...

Mahalo, Walter, for the heads-up.

I am glad John posted that article.