Monday, 9 November 2015

109 St Saskatchewan Drive intersection in detail

I made a post a little while ago throwing around the idea of redesigning the 109 St Saskatchewan Dr intersection with simultaneous green. If you have not seen it, go and view it here.

OK, so to get an idea about what this intersection does and who can go where, lets look at the approaches.

88 Ave is a low volume minor access road, one way for motor vehicles, going westbound. There is a counter flow lane for cyclists going eastbound. It could be used as a through route to get to the UofA.

109 St is a major artery, linking the south side with downtown, with one of the relatively few southbound crossings of the river in this area. It is well used. It is also home to a popular bus route #9, so popular is needs articulated buses even every 15 minutes during off peak times. There are many businesses and shops and a few apartment buildings and bungalows next to the street.

The High level bridge is an old 2 lane southbound only bridge, with shared use paths on both sides. A streetcar runs on the top, and there are discussions on how a low floor LRT could cross here to link Garneau and Downtown.

Walterdale Hill road is a 2 lane northbound only road, with a shared use path on the north side. It is one of two roads that links the Walterdale Bridge, currently being replaced, and the Kinsmen sports centre.

Saskatchewan Drive is a minor artery, and links Scona Road with 104 St. But that is well to the East. It also has a number of high rises. A shared use path is on the north side. It links to Queen Elizabeth Park Road, which also links to the Walterdale Bridge and Kinsmen Sports centre.

OK, now that we know where the roads go, lets see where they come together. Right now, it is a mess.

Lets sort out the problems one by one. First, a protected bike lane on 109 St. And given the congestion here, and the popularity of the #9 bus route, we should also add bus lanes. Cross section of that here:

On 88 Ave, we have a route that functions as a main cycle route in a minor residential street. The Dutch already know very well what to do with that. Fietsstraat time! Literally translating to bicycle road. Because this is an urban minor residential street, that means a 30 km/h speed limit. It is one way for motor traffic but two way for bicycles. Lets not change that. It will have a surface of smooth, red asphalt. About 30-50 cm of beige bricks on either side of the road, so that car drivers think that they have less space than they actually have. Lets add a 2 metre wide counterflow lane, and a small raised but possible to traverse brick median between the two directions, about 20-120 cm wide. There will be raised intersections, but yield signs arranged in such a way that the cross streets yield to 88 Ave. Between access roads that should become unusual for an access road to have the right of way over another access road, but main routes for bicycles are excepted. It will be continuous, all the way to 112 St, either as a bicycle street or cycle path.

Lets add wider pathways and separate sidewalks to the remaining approaches. At least 3 metres, preferable width of 4 metres for the pathway, and 1.8 minimum, 2 metres preferable width for the sidewalk. Try to have separate sidewalks and pathways here. A small raised curb or verge with grass will work well to separate cyclists and pedestrians. Lets also add 40 km/h speed limits to Saskatchewan Drive, Walterdale Hill Road, 109 St and Walterdale Hill Road. Also bus traffic light priority system. That would be helpful.

OK, we have the approaches ready. At the intersection itself, the bicycle street 88 Ave will have a transition from mixed cycling with motor traffic to a cycle track. But the big part is the traffic light programming. The middle of the road is freed up, the curb is taken away, and you can cycle in the middle. On green of course. There are no motor vehicle turns on red allowed. Three simple traffic light signal stages are used. Southbound High Level bridge, right turns into 88 Ave, thru to 109 St, left turns to Saskatchewan Drive and Walterdale Hill Road. Next, High level bridge right turns into 88 Ave and thru to 109 St, and also Nouthbound traffic from 109 St, onto the Walterdale Hill Road and Saskatchewan Drive. Finally, a simultaneous green stage. Each lasting about 20 seconds. Cycle time, 60 seconds plut clearance intervals. If the cycle traffic gets really busy, there can be either a longer simultaneous green stage, a whole second stage, one after each motor vehicle stage, or both. The waiting times are 40 seconds maximum, plus clearance intervals. If you add waiting time indicators, it should be a pretty easy to navigate. It has fair cycle timings. Allows for formerly awkward turns, and pedestrians and cyclists come into much less conflict.

I hope you can see the logic of this within the wording, but I also recommend this David Hembrow blog post to read more about SG (simultaneous green)

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