The White Cane Law
There's a law, called the White Cane Law, that's supposed to protect white cane users, as well as guide dog users. It varies from state to state, from country to country. But the main premise is: keep an eye out for blind* people, cause they can't keep an eye out for you. So rather than comparing the details of one state or country's law to another's, let me just lay out the practical applications for this (or these) laws.
1) Most blind people can hear cars, most of the time. For the most part, blind people can hear you coming. Engines make noise and that noise can be pinpointed to a certain location. So generally speaking, blind people aren't nearly as oblivious as they're thought to be. Of course, there are some exceptions. A blind person may not be able to hear you if:
a. It's really noisy. Noise is the auditory equivalent of fog in your visual field. Trying to pinpoint a specific car in a noisy area is like trying to pinpoint a specific mountain in a distant mountain range on a foggy day. So blind pedestrians may not be able to hear your car specifically.
b. A silent engine. If your car makes very little or no noise, a blind person can't hear you. A guide dog might mistake you for a parked car if you're stopped at a red light.
c. Sound shadow. You might be in a "sound shadow," meaning that the noise your car is emitting might be blocked by another car or building between you and the blind person. In this case, they won't be able to hear that your car is there.
d. The blind person might also be deaf/hard-of-hearing or not be accustomed to relying on their hearing for navigation yet. In either case, the (deaf)blind person can't hear you. (In some countries, a white cane or white cane with a red tip indicates a hearing-blind person, and a striped red-and-white cane indicates a deaf-blind person. If the pedestrian has a striped red-and-white cane, or a guide dog with a red-and-white harness, it means they are both deaf and blind.)
e. Blind people, just like sighted people, sometimes get distracted, either by another outside stimulus or by their own thoughts. In general, blind people are in the habit of paying extra close attention as a way to compensate for their vision loss, but getting distracted happens to the best of us.
2) Most blind people know where they're going, most of the time. If you see a blind person walking, chances are they know exactly where they're going. If a blind person is lost, they know to ask for help. If a blind person doesn't know an area well, they know to arrange for help. If a blind person is alone, it's because they feel comfortable traveling alone. Just let them be, unless:
a. They ask for help.
b. They look lost (walking back and forth, standing still with a confused expression on their face), in which case, offer help. If they accept, then help. If they decline, then let them be. They might want to try to figure it out on their own, or they might just be waiting for someone.
c. There's an obvious temporary obstacle ahead. Something like a construction site might not have been there the last time they were here. A cane will find it and a guide dog will guide around it, but if it requires crossing the street a block ahead or at an intersection that has been moved from its original place, it's helpful to let them know. If it's a big puddle, it can be circumnavigated on the same side of the street and a cane or dog will find it, no problem.
Whatever you do, don't call the cops (unless the blind person is doing something illegal)! This may seem obvious, but it happens to me all the time. (My local police department told me they get calls about me on a daily basis.) So just wanted to put that out there.
3. Blind people have the right of way. If a blind pedestrian starts crossing the street, stop. Even if it's your light. Obviously they thought it was theirs, so let them cross. The time this happens the most often is on turn signals, where it's either green for both of you, or it sounds like it's green to them. Turning cars sound like they're going straight at first, which is the auditory cue for a green light. If a blind person starts crossing on a turn signal, don't turn! You could end up snapping their cane in two, or injuring them, which is way worse than pissing off the drivers behind you who also want to turn. Some major exceptions here are:
a. Don't stop on a green light to let a blind person cross who hasn't crossed yet. There's two reasons for this. One is, they already know it's your light, which is why they're waiting. Secondly, if there is more than one lane to the street, while you may have stopped for them, another car might come zooming because, well, it's their light. And they might not have the reaction time to stop for the blind pedestrian. This is one of the most common ways that blind people get killed crossing streets, so do yourself and them a favor and don't stop for them on your light if they haven't started crossing yet!
b. At an intersection with a stop sign, if they know you're there but aren't crossing, it's because most likely because they want you to cross first, so that they can ensure the road is clear and that you won't start going when they start crossing. It might also be because they're waiting to cross the other way, are debating which way to go, or they don't intend on crossing at all. If it looks like the blind person is aware of you being there but they aren't crossing, just go ahead.
Just some other miscellaneous tips that aren't necessarily about the White Cane Law, but that are relevant to street navigation.
1) You can offer to help a blind person cross the street but don't insist. If they decline, just let them cross alone.
2) If they accept your help, let them take your arm. Don't grab their arm. This scares the living crap out of people. And definitely don't grab their arm before offering help at all.
3) If a blind person asks for directions, don't use the terms "here" and "there," or "this way" and "that way." Words like "this" or there" only make sense when you're pointing somewhere, and the blind person can't see you pointing, so these words are useless. Use words like "straight ahead," "left," and "right."
4) While some blind people do have residual vision, since you don't know exactly how much the person you're talking to sees, use reference points that they can make use of. Don't tell them "it's the building with a blue and white awning." Tell them something like "it's the very first building on the block," or "it has some steps leading up to the entrance."
5) If the blind person doesn't respond to your offer, it might be because they are deaf/hard-of-hearing. Try waving your hand directly in front of them (respectfully). (The most common cause of deaf-blindness is a condition that causes tunnel vision and hearing loss, so they may be able to see you if you're directly in front of them.) If that doesn't work, try touching them lightly on the hand or tapping them gently on the shoulder. If they then respond and it turns out they are deaf-blind, let them tell you how to communicate with them. There are many ways of communicating with a deaf-blind person, but each person uses a different method, so just leave it to them to tell you what method to use.
*blind for the purposes of this post mean anyone with a significant visual impairment, whether partially or totally blind