In two consecutive issues of the estimable Southwest Cycling News (print) publication, I have seen the picture below.
18 mph Albuquerque sign
Editor Fred Meredith shot the photo of the sign on a bicycle boulevard — a low-traffic, residential street configured as a through route for bicyclists — in Albuquerque, New Mexico while attending the 2010 League of American Bicyclists National Rally. Meredith wears more than one bicycle helmet — he also works under contract for the League’s education program, so it is natural for him to attend the National Rally.
Now, please don’t get me wrong, I’m an instructor in the League’s program, and I’m also a proponent of bicycle boulevards and of low speed limits on residential streets. Many European residential streets have a similar speed limit. and so do some streets in Montréal, Québec, in Canada — as per the sign on the left in the photo below.
Some signs in Montréal, Québec
Similar speed limit, what? That sign reads 30!
Yes, it does: 30 kilometers per hour. Canada changed its speed limit signs from miles to kilometers in 1977, conforming to the rest of the world, the only major holdout nations being the USA and the United Kingdom. Part of Canada is French-speaking, the kilometer is a French invention, and that might have something to do with Canada’s divergence from its southern neighbor.
So, anyway, American bicycling advocates on pilgrimages to Europe see the 30 km/hour signs, which look like a good idea to them, and decide to transplant the idea back home.
As I said, I support lower speed limits. I have a few problems with the sign, though.
First of all, our bicycling advocates appear to be math-challenged — or perhaps they want to go a bit lower on speed limits than the Europeans.
30 km per hour converts to 18.64 miles per hour, rounded to the nearest 1/100th. Rounded to the nearest whole number, then, it’s 19 miles per hour — not 18.
There’s another problem with the number 18 — or for that matter, 19. Have you ever before seen a speed limit in miles per hour with a final digit other than zero or 5 — or in kilometers, with anything other than zero? No, you haven’t. There are a couple of reasons. The steps in speed limits need to be large enough to be meaningful. Also, a zero and a 5 look so different that they are very unlikely to be confused with each other at a glance, or if a sign is damaged or partially obscured. An 8, on the other hand, is easily confused with a 3, or a zero. A 9 is easily confused with a 2 or a 7.
The requirement that speed limits go by jumps of 5 or 10 is written into US standards documents. The US standard, the Manual on Uniform Traffic Control Devices, section 2B.13, includes the following wording:
The speed limits displayed shall be in multiples of 5 mph.
Am I nitpicking by raising these issues? I don’t think so. Confusion makes a speed limit harder to observe, and harder to enforce. So do speeds which must be estimated, between the markings on a speedometer. Failure to observe standards exposes governments to liability risks. A nonstandard speed limit can give speeders and their lawyers a legal loophole.
The issue is similar to the one with bike lane color that I described in an earlier post.
The usual school-zone speed limit in the USA is 20 mph. It is only slightly higher than the European and Canadian 30 km/hour speed limit, and it conforms to US standards. This same 20 mph speed limit is already being used in residential neighborhoods in the USA. If 20 mph is too high, 15 also is possible, and I have seen it, in parking lots and the loading/unloading areas of airport terminals.
Advocates of an 18 mph speed limit are acting in disregard of existing American standards which would give them very nearly the same speed limit, on a sign that is more readable and immune to legal challenges.
When and if the USA goes over to speed limits in kilometers per hour, the current speed limits will be adjusted up or down slightly so the numbers end in a zero, as in other countries.
If the USA makes the conversion, a large number of “speed limit 30” signs will become available for re-use as 30 kilometers per hour, and the bicycling and neighborhood safety advocates can expect to have the genuine European speed limit at a bargain price. I will support them in that.