I have noticed on multiple occassions that cars either ignore or do not notice that there is a separate left-turn light for northbound cars on 15th St. This is a serious danger for pedestrians, as well as cyclists using the two-way bike lane. I was nearly hit by a car on more than one occassion because it did not observe the red light. I recommend that a sign reading "Left turn on [green arrow ] Only" be installed at this light and other lights on 15th st where northbound cars have a separate left-turn signal. The situation on 15th and N requires the most immediate attention due to the frequency of cars making illegal turns.