There's an intersection in Berkeley where cars, pedestrians and bicyclists live in uneasy proximity and unintended cooperation. The main street, Ashby Avenue, is a California state highway that never made it to the freeway status that highway planners had intended in the 1960s, and so remains one lane in each direction. In the afternoon, parking on the eastbound side is prohibited for two hours so cars may also use the curb lane on their commute headed away from expensive-living San Francisco and toward the cheaper eastern suburbs.

The north-south street is a relatively quiet residential street that happens to be designated by Berkeley as a bicycle boulevard, which the city defines as "a bicycle priority street," further described on Berkeley's Web site as "a street where all types of vehicles are allowed, but the roadway is modified as needed to enhance bicycle safety and convenience."

This particular bike boulevard, Hillegass Avenue, sees a lot of bicycle traffic. Five blocks north of Ashby lies People's Park, and four blocks further is UC Berkeley, the northern destination of the bike boulevard. Less than a mile south of Ashby is a regional rapid transit rail station reachable by the bike route, which then continues a few miles further south to downtown Oakland.

Two blocks east, College Avenue runs parallel to Hillegass, and is the most congested street in town. Buses are chronically late but brimming with passengers anyway. Three blocks west, Telegraph Avenue runs roughly parallel to Hillegass, two lanes in each direction. It's busy, but not as jammed as College.

Staff of local bus operator AC Transit, which runs buses on both streets but not on Hillegass, wants to claim a lane of Telegraph in each direction to run dedicated Bus Rapid Transit (BRT) lanes. AC Transit's Environmental Impact Report (EIR) predicted somewhat more congestion on Telegraph if this occurs. (College is pretty much maxed out already.)

Many local residents expect some of that traffic to find its way onto Hillegass. Today, the lack of a traffic signal at Ashby discourages motorists from using Hillegass as an alternative to either College or Telegraph, but given enough misery due to congestion on Telegraph, it's inevitable that this bike boulevard will see more cars, contrary to city intentions. But AC Transit's EIR, full of lots of computer models, didn't consider how many motorists might switch to Hillegass.

Meanwhile, UC Berkeley is rapidly expanding the number of automobile parking spaces on campus to accommodate new facilities, and to the south, the state is planning to eliminate a highway bottleneck at the Caldecott Tunnel, widening it from six lanes to eight. The combination of the new parking and the wider tunnel will funnel even more car traffic headed for the UC campus from the east onto College and Telegraph – and probably Hillegass.

The irony is that the local bicycle coalition, which has the most to lose if bicycling becomes more inconvenient on Hillegass, is on record as not only supporting Telegraph BRT, but also a signal at Ashby and Hillegass. There have been no fatalities at the intersection, but many vehicle-vehicle fender benders and near misses between cars, bikes and pedestrians, especially when the main eastbound lane is bumper-to-bumper and cars zoom along next to them in the temporarily-freed-up curb lane.

Today, motor vehicles tend to yield to Hillegass pedestrians but not bicyclists, so many bicyclists dismount and walk across Ashby. A signal would more regularly and predictably stop Ashby traffic, but it would also act as a north-south motorist-magnet as pressure on Telegraph and continuing misery on College lures more motorists onto Hillegass.

Other parallel streets – not bike boulevards – have motor vehicle diverters, such as bollards or right-turn-only rules, but Berkeley now has so many of them, there's a moratorium on installing new ones in the city. In fact, Hillegass is the only north-south street of any length between College and Telegraph to lack diverters. Around town, the city keeps adding traffic circles, which slow motorists, but also force them into bicyclists' paths and don't necessarily reduce car trips.

Perhaps when the EIR process completes next year, the Hillegass bike boulevard will get some protection against simplistic signalization or an influx of cars. Until then, the bike riding remains relatively easy, and the intersection is a demonstration of the traffic calming effects of not adding a traffic signal, as cars, bikes and pedestrians maneuver around each other, mostly with caution.

Scott Mace writes the blog Urbification: Taking the sub out of California suburbs, at http://urbification.blogspot.com