I was riding to downtown Sunnyvale today and got passed by a couple cars while sharing a lane. Absolutely nothing notable about it from a traffic standpoint, except that for several of them I was checking my rearview mirror as they came up and I found that I had an instinctive fear as they approached, almost a startle reaction, in spite of the fact that I could see that all was well. This is unusual for me, in part because I know that strike-from-behind accidents are only around 4% of car-bike accidents (largely at night with unlit cyclists), much less than many other kinds, notably left-cross and right-hook accidents, and in part because my experience accords with that — risky passing is not uncommon, but it’s usually clear that the driver knows where I am, but just doesn’t know that they shouldn’t be that close to me in case I move for some reason.

Nevertheless, overtaking accidents are a disproportionately common fear among potential, new, or inexperienced traffic cyclists, to the extent that many people prefer separated paths in spite of the fact that statistics suggest that in urban environments they increase intersection conflict significantly while reducing only the infrequent overtaking collisions. People feel safer when there’s a barrier to overtaking. Why?

I speculate that it may be due to something inbuilt. Babies have an instinctive negative reaction to someone “looming” (a large object moving rapidly into their space, especially overhead). And we all also know that if someone is chasing you who means you ill, and they catch up to you, your goose is cooked. Cars overtaking both loom (they are large objects coming into the field of perception at a rapid rate) and chase.

In spite of knowing about the low frequency of overtaking collisions, I usually¹ feel safer on bike-laned roads than on shared-lane roads where the lane is marginal for sharing (wide, unstriped shoulders feel the same to me as bike lanes — also interesting to note). It feels like I have my own space, into which the other person is not likely to move without a sign of some kind.² So even I’m clearly subject to this fear, despite my experience and statistics telling me that it’s not proportional.

I would suggest that whether or not it’s true that this fear has some deeply-rooted basis, this might be a useful way to approach the people who fear this. Rather than dismissing their concerns blithely with “not backed up by statistics”, say “I understand that this situation feels really threatening to you. I even agree that it can feel that way. However…”

Both actual safety and the perception of safety are important. Without the perception of safety, people will not engage in desired behavior (like walking and cycling). But perceived safety shouldn’t conflict with actual safety (ideally at all, but in practice, excessively). Given city setup and cycling practice in the US, sidepaths are generally a terrible idea even if they ‘feel’ safer.

¹There are exceptions, mainly bike lanes that are partly in the door zone. The stretch of Old County/Pacific in San Mateo County that feels least safe to me is the section with bike lanes, because I feel that the possibility for conflict is greater if I choose to ride out of the bike lane (as I often do). Ditto Lytton Ave in Palo Alto (feels less safe than University) and Middlefield Rd in the block right before Montrose heading toward San Antonio.

²LAB teachers and religious VCs will here say “You’re clearly too far to the right then, because with proper lane positioning you communicate to drivers that this is your lane.” This may be true in some cases, but I would also note that you can only communicate with people who are receptive to your communication. My observed experience is that my lane position can help or hurt, but that overall people behave more inconsistently around narrow shared lanes, especially those with varying or marginally wide width. And inconsistency is scarier than predictability — which is the whole of the VC mindset!

And as far as passing in adjacent lanes feeling safe or not, it’s rare for cars to be passed consistently, repeatedly, with high speed differential in the adjacent lane because car speeds are normally roughly comparable. When the speeds are not comparable, such as on a freeway at rush hour when the HOV lane is running 65 and the regular lanes are running 25-35, sit in the leftmost travel lane trying to merge and try telling me you don’t feel threatened by the looming, chasing cars.