Every Sunday for the last couple of months I have driven down 100 Avenue, so I know firsthand just how bad the potholes on that street are. Every week they seem to get worse, but not evenly across the street. Some places are far worse than others. It got me thinking – why are some areas of 100 Avenue so rough while others are smooth?

I considered the section road from 170 Street east to 149 Street. Closer to 170 Street there definitely seem to be few, if any, potholes – for the most part the road is smooth. Right around 163 Street, the potholes get really bad. For a while there was a pothole big enough that I’d describe it as a crater! As you approach 149 Street there seem to be less, but still more than the section closest to 170 Street. Why aren’t there potholes along the entire route?

My first thought was that perhaps the traffic volumes are significantly different for each part of the street. Fortunately, the Open Data Catalogue contains average annual weekday traffic volumes for the period 2006-2011, so we can find out. Here’s the result:

Unfortunately there isn’t data for the part of the street closer to 149 Street, but I can’t think of a reason it would be much different (especially since there is nowhere to go but north or east once between 149 Street and 156 Street, more on that in a minute). So it doesn’t appear that traffic volumes would have had much of an impact on the number of potholes.

My next thought was around the maintenance of the street – maybe sections were repaved at different times. I asked the City of Edmonton on Twitter, and was very happy to receive a response:

That actually aligns really well with my empirical evidence! The newest section of road, from 163 Street to 170 Street, is in good shape. The oldest section of road, from 156 Street to 163 Street, is in really rough shape. And the middle-aged section, from 149 Street to 156 Street, is a bit better. Clearly there seems to be a connection between the age of the street and the number of potholes it contains, at least in this example.

Remember that crater I mentioned? It was located right around 161 Street. Here’s what it looked like on April 16, 2013:

And here’s what it looked like in May 2012, courtesy of Google Street View:

Looks like this is one of those potholes the City patches every year! Given that the street hasn’t been repaved in nearly 20 years, perhaps it’s time?

There are a few other interesting things to note about 100 Avenue. If you haven’t driven down there in a while, take a gander on Google Street View. Here’s a quick summary:

• From 170 Street to 163 Street, there are four lanes of one-way traffic (east). For most of this section, there are sidewalks and commercial property on either side of the street.
• From 163 Street to 156 Street, there are two lanes heading east, one lane heading west, and one lane of parking on the north side. There is residential on either side of the street, with a sidewalk on the north and a sidewalk separated by a landscaped buffer strip on the south. Traffic is restricted from turning south.
• From 156 Street to 149 Street, there are two lanes in either direction (though in some places the west-direction is down to one lane). There is residential on either side of the street (except for a few strip malls on the north), with a sidewalk on the north and a sidewalk separated by a landscaped buffer strip on the south. Traffic is restricted from turning south.

One of the things you’ll notice as you drive down the street is that all the potholes seem to be on the south lanes where traffic is going east. No doubt this is due in part to traffic volumes (there’s a lot less traffic heading west). But I have a hunch that there’s more to it than that. I think there are two key features that contribute to the potholes, especially for the section between 163 Street and 156 Street.

First, I think the lane of parking on the north prevents potholes from forming there. Remember that you need water and traffic to create potholes. Even if the water drains toward the sidewalk as expected, the parking lane prevents the vast majority of traffic from causing potholes. Second, I think the landscaped buffer on the south encourages more water pooling. With less sun to melt the snow, more soil to hold the moisture, and more traffic, it’s no wonder that more potholes appear there. It seems there is so much water, in fact, that it overwhelms the drains in the area.

I read the consolidated 100 Avenue Planning Study, and discovered there were good reasons for that landscaped buffer strip:

A number of concerns have been identified with respect to the impact of the 100 Avenue roadway improvements on the neighbourhoods of Jasper Place and Glenwood. These include traffic noise, speeding, pedestrian safety, and the possibility of traffic shortcutting, north-south between 95 Avenueand 100 Avenue.

The Stony Plain Road/100 Avenue Facility Planning Study, approved by Council on January 8, 1985,  recommended that these problems be dealt with by the installation of pedestrian crossings, the closure of some local streets south of 100 Avenue, and the development of a landscaped buffer strip along  the south side of 100 Avenue.

The study did mention that the existing stormwater system was “inadequate” but I’m not sure if or when that was originally addressed. I’m sure the authors of the study weren’t thinking about the possible impact of the design on potholes, but we can see the effects today.

All of this just reaffirms to me the complexity of the problem! Solving the pothole problem will have an impact not just on the way we maintain streets, but how we design them too.