Maybe the responsibility (and liability) for accidents due to weirdly designed or badly marked lanes would have to fall upon the municipality. You could make an analogy to trains: if a local government commissioned a rail line that included a junction that can't be navigated without derailing 1% of the time, you would not blame the trains for not being able to deal with it.

Another analogy could me made to data entry: you could allow free-form text input and try to process all of the long tail of unexpected inputs, or else set out a format that the data has to follow and enforce validation at the input.