Let me start with an admission: yesterday, while riding a bike, I slowed down a car.

Riding through the Presidio, I descended Lincoln Boulevard from the Golden Gate Bridge to Baker Beach at 25 m.p.h. This stretch of Lincoln has no downhill bike lane, just “Bikes May Use Full Lane” signs and sharrows reminding bicyclists to ride in the center of the lane. Lincoln has a 30 m.p.h. speed limit, meaning the driver behind me, who like nearly all road users was courteous and didn’t honk or complain, could have traversed this 1-mile stretch 30 seconds faster if I didn’t exist. (30 seconds might sound like nothing, but Bay Area governments routinely spend tens of millions of dollars rebuilding roads because of delays on this scale.)

Bike advocates often feel the need to spend time, energy, and ink proving that bikes and bike infrastructure usually don’t slow down cars. The Active Transportation Alliance featured the claim that bike lanes slow traffic as a top biking myth to debunk in a recent article. Traffic studies in Manhattan and Chicago, widely publicized by People for Bikes and other advocacy organizations, have found that protected bike lanes have either had no effect on traffic speeds or led to slightly faster traffic even when general traffic lanes were removed to build the bike lanes. Research consistently shows that the primary causes of slow car traffic are too many cars and poor street design and that just adding lanes doesn’t solve the problem.

Disproving the claim that bikes and bike lanes always make car traffic slower is important, especially when people with big audiences continue to blame safety improvements for gridlock, but let’s not lose sight of another important point: sometimes bikes do slow down cars, and that’s okay. I chose the Lincoln Boulevard example because it’s easy to quantify, but there are plenty of other times drivers would go faster if people biking didn’t exist, and bike advocates shouldn’t feel the need to hide this fact. Overemphasizing the fact that bikes usually don’t slow down cars risks implicitly accepting the notion that bikes and bike infrastructure are okay only if they don’t slow down cars.

Slightly delaying other people isn’t specific to bikes, after all; it’s just a fact of life in a world with other people in general and life in a dense city in particular. When I’m in line at the grocery store, for example, the person behind me would get to buy her groceries more quickly if I weren’t there. Out on the road, 21% of all cars are white and 8% are blue, so it wouldn’t be wrong to say that blue cars are slowed down by white cars; if all those white cars suddenly vanished, the blue cars could go faster. But the shopper in back of me doesn’t demand that I step aside so that she can get her groceries faster, and blue car drivers don’t argue that white cars clog up the road and should get out of the way. To think otherwise, to believe that other people should get out of the way, or off the road, simply because they’re other people, requires a kind of mildly deranged solipsism.

Local governments often encourage exactly this kind of thinking among drivers, however. The widely-used Level of Service metric, for example, grades intersections from A to F, and an intersection gets an A if a driver (Level of Service ignores people walking, biking, or taking transit) can go through at full speed, as if there were no other road users in the area, as in the car commercials that warn: “Closed course. Do not attempt.” A cloverleaf interchange in the desert is an A; 24th and Mission is an F. Level of Service is harmful not just because it encourages cities to make their streets more like desert freeways; it also encourages drivers to think that cities have failed them, and owe them an apology, when conditions don’t match the car commercials. There are, in fact, benefits to slower traffic: 90% of pedestrians hit by cars moving at 20 m.p.h. survive, compared to 15% of pedestrians hit by cars moving at 40 m.p.h., and research shows slower speeds help businesses. This is not to say that slower is always better (we don’t need 1 m.p.h. traffic), but rather that, when we’re planning urban streets, the speed at which a driver could hypothetically go if there were no people around is just not a relevant comparison.

San Francisco is, fortunately, abandoning the Level of Service metric, but the bizarre and destructive mentality behind it, that each driver ought to be able to go as fast as he would in an imaginary alternate universe empty of other people, is widespread. Even bicyclists often end up internalizing the idea that drivers must not be slowed down. In their efforts to avoid slowing drivers, bicyclists can inadvertently put themselves at more risk, for example by riding at the very edge of a narrow lane even when, as on Lincoln Boulevard, signs and traffic laws encourage them to ride in the safer center of the lane.

Often bike infrastructure is, as the Chicago and Manhattan studies found, a win-win, giving bicyclists dedicated space while easing car traffic by encouraging more people to bike and improving street patterns. But some improvements for biking and walking conditions, such as re-timing traffic lights to let pedestrians start crossing before other traffic, and, yes, even some bike lanes, do slightly slow down cars, and biking and walking advocates should be more comfortable admitting this forthrightly and arguing that safe access to the streets for everyone is more important than a slight delay for some.

The idea that bike infrastructure is acceptable only if it doesn’t delay drivers makes the process of building bike infrastructure unnecessarily—and dangerously—slow and expensive. Berkeley officials last year delayed striping a planned bike lane on Fulton Street because they didn’t have time or funding to do a traffic study to see if the bike lane would slow drivers, and earlier this year Megan Schwarzman was hit by a car while biking there and severely injured. The right response to this preventable tragedy is not that Berkeley should have found a way to do the traffic study sooner; Berkeley should have striped the bike lane as soon as it became clear it was needed, because people’s safety walking or riding down this street is fundamentally more important than a risk of slight delay for drivers. This is the central point of Vision Zero, which San Francisco and other Bay Area cities have enthusiastically adopted, in name if not always in spirit.

As Megan recovered in the hospital, Bike East Bay launched a campaign to get the delayed bike lane on Fulton built, and earlier this month the Berkeley City Council approved a plan to complete it by May. The city is still planning a traffic study on Fulton, but now the study will take the bike lane as a given and then look for the most advantageous way to use the rest of the space. This is the right approach and one that local governments and bike advocates alike should take as a model: look for the most efficient ways to use our streets, but start from the assumption that all of us have a right to be on the road, safely, even if drivers could go faster if they had the road all to themselves.