I've spent a lot of time lately thinking about the widths of bike facilities and how much width we need for a given type of bike facility. While design manuals give you values for the upper limits, lower limits, practical lower limits, absolute minimums, its not always so straight forward when faced with a constrained right-of-way. What is the user experience on facilities of different widths? Lately I've been out with a tape measure to better understand this.
Lets start with the guidelines, the go to guideline in Canada is the recently updated Transportation Association of Canada (TAC) Geometric Design Guide (GDG) for Canadian Roads which as of last year, has a whole new chapter on bike facilities. It generally recommends a lower limit of 1.8m and upper limit of 2.1m for a uni-directional bike facility, increasing to 2.5m for a protected facility. The practical lower limit is generally 1.5m, but in the small print there is an absolute minimum of 1.2m. 1.2m is the same as the general operating envelope for a cyclist, i.e., the width of the bike and rider, which i'd estimate varies between about 0.6 to 1.0m plus a bit of wiggle room.
Recently I found myself riding along a pretty narrow uni-directional bike path (the one above on 10th Avenue in Vancouver) adjacent to a colleague having a conversation as we were riding along. It occurred to me that this was a pretty narrow bike facility but we were riding reasonably comfortably side-by-side. We stopped and measured, and the asphalt surface of the bike path was just 1.2m. Seconds later, another couple rode by on dutch style upright bikes side-by-side also having a conversation (was too slow to capture this), and a little later the two in the photo below also rode by almost side-by-side. I waited for a better photo, but had to move on. Apologies for the poor iPhone markup to remind myself of the width...
Anyway, here we were with multiple examples of riding side-by-side on a 1.2m protected, separated, whatever you want to call it, bike path. This doesn't fit with the guidance in the manual.
There are of course some reasons for that. First, the edge condition either side of the asphalt in this example were low profile rollover curbs. This gives you comfort that should you need to veer off the path, you can do so and will be fine. There is no 6 inch raised curb to knock you off balance.
Secondly, in my personal experience on the above bike path, and the two examples that followed, both cyclists new each other. Had I been riding alone, I would likely have been in the middle of the path, making it more difficult for someone behind to pass. However, by ringing a bell or calling out, I could feasibly move over and they could pass on the 1.2m bike path.
I guess lastly, the volume of cyclists was not excessive enough to justify a wider path, if space was even available, and volumes of pedestrians were also relatively low, suggesting limited conflict between modes, if a cyclist did have to stray off the bike path. Where volumes of both cyclists and pedestrians may be higher, greater separation may be necessary.
Bottom line, if you have a severely constrained right-of-way, 1.2m does allows for two people to ride side-by-side, and squeeze by, if the edge conditions allow cyclists to track close to the edge of the path with little consequence for any errors.
If the edge conditions do not allow for errors, then we need to allow some extra space. If we want to allow comfortable passing without the need to ring a bell or yell, we need more space. In this case values closer to the TAC upper limits are still preferable.
I leave this post knowing in those extremely constrained street retrofits including bike facilities, with the right edge conditions, narrow widths can work reasonably well. I'd still rather be riding the facility above than on-street mixing with cars.