On open metal grate bridges

It’s raining as I write this which means many bicyclists in Chicago who want to travel over one of the 25 open metal grate bridges without a bike-friendly deck treatment have to decide: risk the slippery conditions on the bridge that cause your bike to feel wobbly and possibly fishtail, or ride on the sidewalk across the river.


A photo I took last night showing the new anti-slip metal plates over the bike lane on the Kinzie Street bridge. These plates cover the metal grates that make bicycling dangerous, especially when wet. 

Riders no longer have to make that choice today if they bicycle through the Kinzie Street protected bike lane as the Chicago Department of Transportation (CDOT) installed a metal deck over the bike lane portion of the bridge. This is the third bridge in two years that CDOT has treated to make bicycle friendly. (The ribbon cutting ceremony is Monday, July 25, at 11 AM, on the southeast corner of Kinzie and Jefferson.) The other two bridges treated recently are Harrison Street bridge in 2009, and Randolph Street bridge in 2011.

But we still have 25 more dangerous bridges. And CDOT knows this.

The beginning of a study

In 2004, CDOT hired T.Y. Lin International to study the inventory of metal grate bridges and their link to bicycle safety. The introduction of the report states:

These metal grate bridges…can be difficult and intimidating for a bicyclist to cross. Depending on the type and direction of the grating, grooves can cause a “channeling effect” or “sliding” for bike tires, and narrow tires can be lodged in gaps between the bridge grates. In addition, the metal can become increasingly slippery when wet, making these bridges even more difficult for bicyclists to safely cross in rain or snow.

The study’s goal was to determine what options are available to make these bridges “bicycle friendly.” (You may want to skip the middle section and read the conclusion at the end – what follows is a reprinting of several lists from the study.)

Rating bridges

Kinzie was rated a “bikeability” of “good,” as was Randolph. Harrison was rated “fair.” I might have rated every bridge “poor” because each of them is slippery, even when dry, and none provides the traction of an asphalt or concrete roadway.

Which bridges were rated poor?

  • Webster (north branch, at Ashland)
  • Cortland (north branch, at Elston) – deck has since been treated
  • Chicago (north branch, at Kingsbury)
  • Wells (main branch, at Wacker) – deck has since been treated
  • North (north branch, at Kingsbury) – bridge has since been completely replaced
  • Clark (main branch, at Wacker)
  • LaSalle (main branch, at Wacker)
  • 18th (south branch, at Canal)
  • Loomis (south branch, near Archer)

The ratings were based on a formula that took into account deck type, grate orientation, percent deck was filled, and observed deck quality. The consultant used the ratings to prioritize bridges for treatment. After applying the formula, 15 bridges were rated as poor or fair. The consultant narrowed the list to find the bridges most in need of treatment by scoring the bridge higher if it was part of the bikeway network, and if it was already included in CDOT’s then-current (through 2008) bridge reconstruction or rehabilitation program. If it was included in the plan to be rebuilt, it was no longer prioritized.


Riding a bike over the treated deck of Cortland Street.

Priority bridges

The final list of prioritized bridges comprised 18th Street, Canal, Chicago, *Cortland, Halsted (North Branch River) and *Wells Street. This was curated from the bridges rated “fair” and “poor.”

The list below is excerpted from the CDOT 2003-2008 bridge reconstruction plan and includes only those bridges slated for construction, and their current status (in alphabetical order):

  • 18th Street – Still bike unfriendly as of 2011
  • Chicago Avenue – Still bike unfriendly as of 2011 (made worse in 2010-2011 because of a construction detour)
  • Division Street at North Branch Canal – Still bike unfriendly as of 2011
  • Division Street at River – Still bike unfriendly as of 2011
  • Halsted Street at North Branch Canal – Currently under construction; it will have a concrete deck, a bike lane in each direction, and two main lanes in each direction.
  • *Harrison Street – Has a bike friendly deck as of 2009
  • Loomis Street – Still bike unfriendly as of 2011
  • *North Avenue – Has a bike friendly deck as of 2008
  • Van Buren Street – Still bike unfriendly as of 2011

Additionally, Canal Street (south branch) was reconstructed in 2010 but a bike friendly deck was not included in the result.


Of the 6 priority bridges, 2 were treated to have bike-friendly decks. Of the 9 bridges slated for reconstruction (some overlapping with priority bridges), 2 additional bridges were treated to have bike-friendly decks. (*Treated bridges have been starred above.)

The study assumed that bridges planned for reconstruction had designs in which it was too late to make bike-friendly changes, or that bike-friendly changes were already in the design – I don’t think either was true. Neither Wells Street nor Cortland Street were included in plans to reconstruct bridges yet later received bike-friendly deck treatments. This may have happened because of Kathy Schubert’s postcard-writing campaign to then-CDOT Commissioner Miguel D’Escoto, the commissioner at the time of this study.

Based on the lack of action to make the prioritized bridges safer for bicycling, it seems CDOT either hasn’t read the study report, or has chosen to ignore the consequences of leaving these bridges as-is. Kathy has begun another postcard-writing campaign to urge CDOT to treat the remaining open metal grate bridges. This issue fits squarely with the two goals of the Bike 2015 Plan: cutting crashes by 50% and getting people to make more of their trips on the bicycle – the obstacle metal grate bridges presents will stymie these goals.

23 thoughts on “On open metal grate bridges”

    1. When I asked for the cost, I only asked for the aggregate total. So $130,000 included “flexposts, green epoxy covering, bridge plates and bolts, modular curbs, traffic control and protection.” I’ll ask again to get the cost of just the bridge plates.

      I don’t know what the hold up is. It could be money. The capital bridge reconstruction plan this article mentions saw very few of the bridges in the plan actually have work done. Did the city ever allocate money to the plan? Did it move money from this budget item to another one?

      According to the plan, the Halsted at North Branch Canal was going to start construction in 2005. But it didn’t start until 2010.

      1. Hi Steven,
        We sort of use Lake as our little highway mostly from Wabash to Peoria then south from the Loop. I don’ttake Randoloh very ofter but will try it again to see. We do the bridge on Lake on the sidewalk as the cars get pretty close there and we are usually coming from a walk/ ride on the Riverwalk if it isn’t a rush hour, very warm our or lunch time. We’ll try Randoplh again so to see how trafficky it feels:). We do plenty of shameless sidewalk riding with kids on their own bikes and on ours especially in deserted tough spots where there are not any pedestrians.

  1. It’s interesting to hear what is going on with the plates on the bridges. Riding with our bikes loaded with kids renders the grated bridges a sidewalk ride every time. I ride over two or three bridges daily on our school run loop home: We sidewalk Cortland even though it’s plated now as the cars can get very close on that bridge, Wabash is easy as it’s all concrete and tends surprisingly to be quiet and our last bridge is Lake which is always on the sidewalk.
    When our guys ride to the loop from home we go over the bridges both ways and they are always on the sidewalk on their own bikes as the cars are way too close and a grated bridge for them is totally out of the question.I wish there was a better solution but sidewalk riding on almost every bridge is our only safe choice if our family is going to be on our bikes.

    1. Thank you for your input about riding on metal grate bridges.

      State Street bridge is also 100% concrete, and can be quiet sometimes, like Wabash.

      How come you guys ride Lake Street on the sidewalk? Next time check out Randolph (when leaving the Loop) because the edges have a 5-feet wide concrete infill.

      As for Lake Street, that seems like a great candidate for a flexible bollard-protected bike lane in each direction.

  2. So what happens when conditions get icy? I hear that can happen in Chicago. Grated bridges would surely tend to break up any ice or snow, whereas a flat deck will turn into a skate park. There’s a big difference between a bike that merely ‘feels wobbly’ and a bike that’s actually traveling on a sheet of treacherous ice. I know which surface I’d prefer to ride on – and it’s not the so-called ‘bike-friendly’ one. And on a bike path that narrow, when cyclists wipe out in winter conditions, they’re more than likely to end up under a 3000lb+ vehicle.

    To me, this seems like yet another brilliant DOT plan to get as many neophyte commuting cyclists as possible into the city morgue. Maybe city planners haven’t yet realized that commuting happens in winter too. A bike is a vehicle, not a toy, and some of us need to use it in all weathers, not just when the temperature is around 70 degrees.

    1. There are two decks: concrete and non-slip metal. When it’s raining or snowing, or has recently, you do NOT want to be riding on the open metal grates. 

      Many people will find a Loop bridge that has a different deck (I mean, not 100% open metal grate) or ride on the sidewalk. The grates may break up ice, and collect little snow, but it’s not the presence of those things that make them dangerous to ride over: it’s the moisture on the metal. 

      Open metal grate bridges are dangerous even when completely dry. To get a visualization of what it’s like to ride over when completely dry, watch this video I recently uploaded about the 18th Street bike lane:

      When you say “another brilliant DOT plan to get as many neophyte commuting cyclists as possible into the city morgue”, do you mean the plan to cover the open metal grate decks when building protected bike lanes?

      1. True, I got a lot of practice riding over open-grate bridges during my long stint as a bike messenger, but I personally don’t really worry much about riding over them nowadays, even when they’re wet. My advice: just stay seated on your saddle, ride slow, and don’t look down.

      2. I watched your bridge-riding video. I’m not convinced. Your video shows a bumpy ride, but not a dangerous one. I’ve ridden over such bridges even in winter and they are not really a problem – you just maintain your line as you do over any undulating surface – nowhere near the problem posed by ice and snow on the ‘preferred’ flat decking that will gather ice and snow and that will be rutted by bicycle tires and never cleared of ice or snow (unlike the road). Do you really think DOT intends to clear snow on these segregated paths, even if they have the vehicles that can clear paths that narrow? Dream on!

        Winter is approaching. Mark my words – you’ll find the decking makes riding over bridges far more dangerous during freezing conditions. By next spring, you’ll be cursing that decking.

        1. Advil (the medicine maker) just donated a truck and snow plow that better fits in the bike lanes. 
          http://thenwpassage.com/?p=2922The bridge decking has been on Wells Street and Cortland Street bridges for at least 5 years each. I’ve not heard about a single complaint or report of a crash on these bridges, but I know of several injurious crashes on open metal grates. Harrison and Randolph Street bridges have concrete infill as their bike-friendly deck. Lake and State streets have 100% concrete decks. Cyclists entering and leaving the Loop often go out of their way to use these bridges. 

          1. “Advil (the medicine maker) just donated a truck and snow plow that better fits in the bike lanes. ”

            I read that it played a major role in the recent snow showers, making a valuable contribution to filling its parking space and preventing snow accumulation there.

            As for the bike lane, I hear snow was allowed to accumulate there as a test of the ‘non-slip’ metal plates on various bridges.

            Glad to see DOT is doing all in its power to maintain the bike path.

          2. How is the plow doing? Was it there alongside the plow that came to remove snow on the regular traffic lanes? Was it out a day later? Two? More? How is the ice that must accumulate on those ‘anti-slip’ metal plates?

            The city of Chicago has sold cyclists a bill of goods. I should think a few more weeks of this should put paid to all the rosy predictions and gleeful cheering of the Fall. Or you could just blindly insist that everything is perfectly fine.

  3. I’m here reading this article because last Saturday I was riding down a metal grated bridge on division before Halsted and I fishtailed out to the left. thank god there were no cars heading in my direction but I ended up locking my bike to the bridge and canning it to st. Mary’s where I got 10 stitches to my knee and two to my elbow. a metal grate went into my knee 🙁 I will never ride over a metal grated bridge again.

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