12 thoughts on “Washing pedestrians”

1. “PedestrianinOttawa” filmed a series of videos of Albert this week too: http://www.youtube.com/playlist?list=PL2A60A4FDAE60BBCF&feature=plcp A sloshing good time.

   1. But there are no pedestrians in the video! Where’s the fun in that?(tongue firmly in cheek)

2. Pedestrians are inconveniences in this city. If we are not dodging cars or puddles, then we are navigating other barriers. Please take a look at Confederation Heights at the entrance from Heron/Bronson to the O-train and government campus. There is a crosswalk at Heron that cannot be cleared of snow/ice because of a light pole in the middle of the path, and a railing along the path from Heron to the O-train that was installed for, apparently, the sole purpose of blocking the shortest and most convenient pedestrian route from the street into the campus. Our planners really should learn to read the tracks in the snow….

3. i had a nice shower on Booth St. today. i’m sure you know exactly where i’m talking about.

4. It was Bell that dug up the street this summer/fall, not the city. Bell typically rebuilds the street exactly as it was before, including any deficiencies (like the 2″ high sidewalk/curb on Elgin at Frank, which was that height after years of cars driving over it and pushing down the sidewalk that was originally the normal height years ago).

5. This problem of pedestrians getting sprayed has deep routes in the way roads are engineered.

   Every good engineer knows that the Romans designed their roads with a cambered cross-section so that they drained from the centre to the outside into the ditches that were dug as part of the road building process. In rural environments without structured drainage, that makes perfect sense to this day.

   The problem is in applying this to an urban environment with sidewalks where there are no ditches but rather drains, though this design by and large works – albeit not well – for the two thirds of the year in which we don’t have snow and ice. The design itself is found everywhere across North America and beyond, so it’s not like it’s been caused by Ottawa’s engineers alone.

   But here in Ottawa and other wintry cities, what happens is that snow is plowed to the outsides of the road against the curb, where it blocks the drains. So long as the temperature remains low enough that snow and ice don’t melt into water, even this will sort of work (note however that melting can occur on sub-zero days that are sunny, or where salt is used in large quantities). But once water is added to this environment of drains blocked by snow and ice, we get a problem.

   The cambered road sheds that water as far to the sides as it will go, which is usually against the snow bank or curb, where it pools since it has nowhere else to go since the drains are blocked. At intersections, pedestrians have to walk through these pools to cross any streets. Between intersections, pedestrians risk being sprayed.

   The solution to this problem is mind-numbingly simple, but it requires that the road engineers completely revisit their design standards for urban cross sections. That solution is simply to turn convex road cross-sections into concave cross-sections with drains down the centreline, rather like what is found in some medieval European city streets which used to have a gutter down the middle. Since the centreline is always cleared of snow, the drains will always remain open. Intersections would feature a single large circular drain in the middle with the entire intersection sloped towards the centre like a dish.

   Besides sparing pedestrians from unwanted washes, this solution also has a few other advantages, namely: (1) with proper drainage, frost damage from standing water will be much reduced; (2) cyclists will no longer have to dodge drain grates and the damaged road surface around them while the centreline drains are less likely to suffer that damage in the first place since the water will be draining rather than pooling; (3) expensive side-inlet or sidewalk drains will no longer be needed; (4) storm sewers can be laid under the centreline with drains dropping directly into them without the need for cross-drains.

   1. Of course you are 100% correct. Alas, in 30 years I have not been able to interest anyone at the city in this road profile, even though we gets little bits of that “drain away from the curb” from time to time, eg rideau bus mall, transitway stations, etc. Now what was the definition of insanity??

   2. Would it be possible to avoid having a drain in the intersection by having it be convex, draining into the concave profile of all four connecting roads?

      The reason I ask is that I’m a big fan of raised intersections. Not 30 km/h speed bump raised intersections, just gradual 3 or 4 inch elevation that visually and physically remind drivers that they are crossing a pedestrian zone.

      1. Theoretically, yes, but the transitions are going to be quite awkward.

         You want to avoid having any convexity where the crosswalks are located because convexity in those locations always opens up the possibility of pooling water due to being trapped by snowbanks or ice dams. That means any transition from a convex shape has to occur within the intersection itself.

         So what you would end up with is an intersection where the “high ground” is shaped like an ‘X’ across the intersection with both the apex and the extremities of the ‘X’ fattened… and that is going to be exceedingly difficult to do in practise.

         You could probably have an intersection with raised crosswalks that are themselves like a saddle in which they shed water towards the centre of the street you’re crossing and then shed it into both the intersection and into the centre of cross street to run down the centreline to the nearest drain (which, frankly, I would put very close to the crosswalk in any concave street profile, though not in the crosswalk since it would constitute a tripping hazard for anyone wearing heeled shoes). The intersection would still be dished, but it would also be rimmed by the raised crosswalks. In effect, the drainage of the intersection would be separate from that of either cross street. This would still be a bit awkward to construct, but nowhere near as awkward as trying to make the intersection convex.

         From the point of view of a motorist, they would have two humps to go over, one at each crosswalk, with the possible exception of a right turn.

6. One advantage of convex roads is that sleepy drivers drift off the road rather than into oncoming cars. This should not be a problem in the city!

7. I use that intersection a lot, and am amazed how engineers were able to replicate the uneven grade differences in their finished product. Just like driving across the pre-construction Booth/Albert intersection!

8. TheCityof Ottawa is too busy builduing a skating rink next to a skating rink to care about people. Courtesy of HRH Watson!

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