Personally it’s crossing the freeway where I live. My city has about 100,000 people but only six roads cross the freeway, with three more wayyy on the outskirts that are basically detours. There are also only a few pedestrian bridges that cross it, and zero pedestrian tunnels. The way our freeway works is it goes around downtown with the ocean to the south and west, so people live on the outside of the freeway and then commute inwards. This means insane bottlenecks with miles of cars in both directions trying to get to the other side. It doesn’t help that our four freeway entrances are also at some of these tunnels / bridges, which means people who need to get on or off the freeway are also present. In general it’s a shitshow and I’d really like to see a few more bypasses to prevent this congestion in the future.
I’m going to give a narrower scope and mention something that bothers me in my neighborhood. I can bike to a park and ride for a bike-friendly train that goes directly to downtown with a decent frequency, which is fantastic! Unfortunately it’s really only accessible by car, and I have to take quite a significant detour to get to it without needing to ride ~a mile on a very fast very busy main road without sidewalks :(. We’re so close!