Today was the first day of a construction detour expected to send thousands of cyclists onto the Bowery from the Manhattan Bridge every day. A temporary bike route extending from the south side of Canal Street to Prince Street was constantly blocked by parked police vehicles, trucks, and cars during the morning rush, forcing cyclists to weave into the stream of Bowery traffic — full of buses and large trucks.

The detour is expected to last for at least six months. As a consequence of cable rehabilitation work, which according to the city will make the Manhattan Bridge bike path unrideable, DOT is directing cyclists to swap places with pedestrians and take the south side of the bridge. The announcement mapping the detour routes went out last Friday [PDF].

The Manhattan Bridge sees the second-most bike traffic of the four East River bike crossings — an average of about 3,000 cyclists each day, according to DOT’s 2010 counts. All was well on the Brooklyn side this morning, and the detour for bridge-bound cyclists on the Manhattan side doesn’t call for riding on any streets that might be especially hazardous for cyclists.

But the Bowery detour was hairy, to say the least. Some sort of physical protection, like Jersey barriers, will be necessary to prevent situations like this, just north of Canal:

North of Hester Street, the route consists of curbside sharrows until you hit Prince. Curb regulations apparently call for no standing in the shared lane from 7 a.m. to 10 a.m. on weekdays (that is unofficial — Streetsblog is trying to confirm the rules). Even when the regulations were in effect this morning, the lane was constantly blocked and impassable for cyclists:

Streetsblog has a request in with the Manhattan Bridge community liaison about further steps to protect cyclists. If the Bowery is going to be the northbound Manhattan Bridge bike detour until January 2012, more must be done to clear the route of obstructions and keep cyclists safe.