Today we started with a light jog, and skated over invisible black ice on the sidewalk. I noticed something about the composition of the sidewalk, and where the ice was. So when a company (or maybe the city?) recently replaced sections of it, mainly due to tree roots, they failed to design their solution for all conditions. Heads up, this is about to get nerdy.
When the project ran, someone made a decision to use flat concrete instead of aggregate, so instead of a rocky textured sidewalk, it would be flat and smooth. To avoid slip risk, the top layer appears to be lightly scored. Although ice and snow are rare, they do occur. What would it have cost to use a similar product to the original? What were the trade offs? Does concrete hold up better against tree roots over time? It’s an architectural problem: concrete does not match the rest of the sidewalk.
I don’t really want technical answers about the sidewalk’s composition, but the project missed a use case: me jogging at five am, when there’s ice. I’m not saying they had to solve for that specific situation, but if ice and snow are possible then does it justify the additional cost? Is the benefit to the jogger worth it? Or was the decision to use concrete made in full awareness of the potential risk, and accepted as a trade off? The value proposition of using concrete must have outweighed the cost to go with original materials. Maybe concrete is the new industry standard surface, maybe the city mandates it for all sidewalk repair.
So now we are left with the architectural debt of that decision. We have to live with the trade off. To replace it again is too expensive, and to replace everything around it with concrete is too expensive. So we have to live with it.
It’s not bad as neither one of us fell over, but it cut the run into a pattern of jogging and walking gingerly over the ice.