Diamonds (and bike-friendly speed bumps) are a rider’s best friend on 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 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.

Map PBOT sent to Michigan Avenue residents.

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? 

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soren
soren
2 months ago

As much as I am annoyed at PBOT for abandoning a 10 block section of the Tilamoook Neighborhood Greenway to aggressive and dangerous SUV drivers, the diamond ground pavement on the replacement route (NE Hancock) is quite smooth.

Lowell
Lowell
2 months ago

I happened upon this last night. It was odd at first because initially it seemed like it was half-completed, where they grinded it down but hadn’t yet resurfaced. But then I came across the speed bumps and I wondered if they messed up by putting them down early.

I like the placement of the cut-outs in the speed bumps more here than in other spots that use them, like Fremont west of Vancouver. They more naturally line up with where I am actually riding. I didn’t have any cars pass me so I’m not sure how they will handle them, but I’m sure car drivers will still position their cars to to align their tires with the gaps.

I generally avoid Michigan because of how terrible the street surface has been. The microsurfacing last year helped, but of course there were still large stretches of really bad road. This is definitely a major improvement, though I’m not sure if there are still sections with bad road surface or not. And it’s still not as smooth as, say, Vancouver/Williams so I will probably still use that as my primary North/South route.

pigs
pigs
2 months ago

PBOT should do SW Corbett Ave next between Nebraska and Laview. It’s terrifying enough going down that street as its a 14% grade. Add in the bumpyness of the old concrete and patchwork, and it feels like the wrong bump will make my front brakes lock up. Corbett is integral to the bike network to go from SW to downtown/eastside as it is the only direct road that isn’t Barbur or Terwilliger.

I’m glad they have to equipment to do it now at least and excited to see them to do it to more of these concrete streets.

fishyfishy123
fishyfishy123
2 months ago
Reply to  pigs

Yeah, that stretch is crummy – hard to believe it’s a bike route. The first time I did it I was so surprised, I just got off and walked. I prefer going down Barbur further and going down Corbett from there. I’d love to see that become a more viable option.

Therese
Therese
2 months ago

I think the FHWA also talks about the gaps being the difference between a speed bump and speed cushions so fire trucks can use easier (can help decrease department resistance to implementation).

nic.cota
nic.cota
2 months ago

I live right next to this!

I had a ‘line’ figured out down this stretch of Michigan from a utility pavement repair patch. If I veered off of it, it was bad news for anything I was carrying (and my spine). It was honestly a barrier for some folks we were trying to introduce to biking on this street.

Glad to see PBOT prioritize this, kudos to the folks at PBOT that made this happen! Its been great way to end our commute home every day

idlebytes
idlebytes
2 months ago

I always assumed those cutouts were for emergency vehicles because they’re the perfect size for a large SUV. My six mile ride home from work includes at least 3 or 4 people that swerve into the center of the lane to avoid the bump usually while speeding. So much fun when they’re coming at me. In my experience the only time drivers comply with these and go over the bump is if they would literally hit another car or maybe a cyclist.

Couldn’t PBOT put something down the center of these bumps to make drivers stay on one side like some of those wands and a raised curb? Then if an emergency vehicle does need to go through it they still can.

Speaking of which the speed bump at 55th and Everett needs to go it’s flat out dangerous. It’s ok if you’re going westbound but eastbound you’re not lined up to go straight through it and hit it at an angle if you’re not prepared. At night a cyclist that’s unfamiliar with it is going to wreck.

Damien
Damien
2 months ago
Reply to  idlebytes

Couldn’t PBOT put something down the center of these bumps to make drivers stay on one side like some of those wands and a raised curb? Then if an emergency vehicle does need to go through it they still can.

Was thinking the same thing. And likewise, the only time I’ve seen these notches not used by automobiles – via swerving – is the threat of imminent head-on collision (emphasis on “imminent”, because I’ve seen some drivers cut it close).

Ray P
Ray P
2 months ago
Reply to  idlebytes

I always assumed those cutouts were for emergency vehicles

That’s exactly what they are for. PBOT even says as much in their own design documentation. Bike usage is never mentioned or implied. Which is why these don’t work as speed bump. They are screwing the design up for bikes when they were never meant to be used this way.

Ben G
Ben G
2 months ago

Saw PBOT working on this last week, need to go try it out.
I hope the grind is great, that section was such an awful patchwork before. Hoping Holman and Bryant are in queue!

Noel B-D
Noel B-D
2 months ago

Speed bumps with the cutouts are useless. The ones they installed on N Willis have cutouts perfectly placed so drivers routinely drive down the middle of the street (on top of the double yellow no less!) so they don’t have to slow down. Has NO effect on the drivers most needing to be slowed down via infrastructure.

FDUP
FDUP
2 months ago
Reply to  Noel B-D

Well, as a cyclist I really resent them also, ESPECIALLY on the greenways; so maybe we need to find new and better ways to slow traffic down? Even a full speed bump w/o cutouts (which aren’t specifically for bikes but sure do help) ends before the curb for drainage purposes and can be at least half circumvented by a determined motorist if no parked vehicles are present.

Concordia Cyclist
Concordia Cyclist
2 months ago

I ride this several times a week and was pleasantly surprised at the improved smoothness. Typically I’ve tried to ride down the middle of the street to avoid the major bumps and cracks, but no longer need to do so as much with the newly ground surface.

Would still prefer a real repave – there are still some tricky cracks on the stretch – but I’ll take it versus the kidney-dislodger it recently was.

Glad I’m not the only one who thought it was only half done.