Diamonds (and bike-friendly speed bumps) are a cyclist’s best friend on the Michigan Ave neighborhood greenway.

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 the street surface itself is just as important as the people with whom cyclists share the street. Large potholes, cracks, and uneven lumps are not only uncomfortable and inconvenient, they can also cause someone to crash or cause other negative outcomes (like shifting cargo or accessories ). Even speed bumps, which bike safety advocates often call for, come at a cost to riders whose bodies and bikes bear the brunt of them through no fault of their own.

PBOT card sent to residents of Michigan Avenue.

These realities forced the Portland Bureau of Transportation to get creative with smoother greenways. Now, instead of adding hardware to the streets, they improve the riding experience by removing it.

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 full repaving. Another new method is what PBOT calls “diamond grinding” where they carve 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 only the second time on a section of the North Michigan Avenue neighborhood greenway between Killingsworth and Alberta. They also added five speed pads (AKA speed bumps) that have notches cut out for riders.

The result is a smoother ride and slower riding speeds, which helps make cycling more comfortable.

According to PBOT, diamond grinding “corrects surface defects and provides a more uniform surface for cycling comfort.” It is most often used on highways, 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 disrepair and provide a very bumpy and stressful experience for cyclists.

Smooth streets are even more important these days, as the overall average speed of bicycle users has increased due to the widespread use of electric motors.

I ride this freshly ground section of Michigan very often and there was always only one tight line I could use if I didn’t want to be thrown around. The new surface feels much better!

As for speed bumps suitable for bicycles, they have received mixed reviews from cyclists in the past. Some people think the notches are too narrow, and others don’t like the way the conductors will deviate to fit into them. PBOT heard these criticisms and tried to adjust the design accordingly.

Have you ridden these before? What do you think?

Wiley C. Thompson