Emergency access failed when housing density overruled road geometry

What is the worst urban-planning failure you have encountered?

One estate made a planned emergency route too narrow for a car, sold the surrounding plots, and then had to move the access and rebuild part of a park.

A housing-estate plan included a pedestrian route intended to double as emergency access, but redesigns narrowed it until even a car could not pass. The conflict emerged after plots had already been sold off-plan, so widening the original route would have disrupted property commitments. Those pre-sales included British homes purchased by buyers from Hong Kong during the transfer from British control and its aftermath. Planners moved the emergency entrance and rebuilt part of a small park instead. A pedestrian bridge had already been reinforced to carry a fire engine, yet the final access arrangement left it serving walkers and cyclists. Adding units without rechecking vehicle envelopes had disconnected expensive infrastructure from its intended safety function.