When we think of what makes a great neighborhood greenway we often think of anything that reduces the speed and/or volume of cars. But just as important as who bike riders share the street with is the surface of the street itself. Large potholes, cracks and uneven bits are not only uncomfortable and inconvenient, they can also force someone into a crash or lead to other negative outcomes (like cargo or accessories rattling out of place). Even speed bumps, which bike safety advocates often push for, come at a cost for bicycle riders whose bodies and bikes bear the brunt of through no fault of their own.
These realities have forced the Portland Bureau of Transportation to get creative when it comes to smoother greenways. Now, instead of adding material to streets, they’re improving the cycling experience by taking it away.
Last year we reported on a new microsurfacing treatment for greenways that allows them to smooth out cracks at a fraction of the cost of a full repaving. Another new method is what PBOT refers to as “diamond grinding” where they trim and level uneven spots and reduce the depth of cracks and small potholes (the “diamond” part refers to the diamond blade in the grinder).
The city recently used this technique for just the second time on a stretch of the North Michigan Avenue neighborhood greenway between Killingsworth and Alberta. They also added five speed cushions (AKA speed bumps) that have notches cut into them for bicycle riders.
The result is a smoother ride and slower driving speeds — both of which add up to more comfortable cycling.
According to PBOT, diamond grinding, “corrects surface defects and provides a more uniform surface for biking comfort”. It’s most commonly used on freeways, but it also works on older streets that have a concrete base. The first place they used this technique was on NE Hancock between 33rd and 37th. These types of streets (NE Holman is another one that comes to mind) are often in terrible shape and give riders a very bumpy, stressful experience.
Street smoothness is even more important these days as overall average speeds of bicycle users have increased due to widespread use of electric motors.
I ride this freshly-ground section of Michigan very often and there was always only one narrow line I could use if I didn’t want to get shaken up. The new surface feels a lot better!
As for the bike-friendly speed bumps, these have gotten mixed reviews from riders in the past. Some folks think the notches are too narrow, and others don’t like how drivers will swerve to fit into them. PBOT has heard these criticisms and has tried to adjust the design accordingly.
Have you ridden these yet? What do you think?