We know that the best way for cyclists to avoid being hit by motorists is to make sure we are seen. We can enhance our visibility through lights, reflectors, bright clothing and lane positioning. Unfortunately, all of this may not be enough to get the attention of a distracted driver who simply isn’t looking.
A lot of riders mount bells on their own bikes. While these may be pleasant sounding and looking, and a great way to signal to other cyclists, many of them are not loud enough to penetrate to the interior of an automobile, where it will likely be competing with music and other traffic sounds. Even if a driver can hear a bell, it may not register as a sound that demands their attention.
A number of companies have started producing horns that can be mounted on bikes. Orp makes a combo bike light and horn, which can make a ‘friendly’ honk for signaling to other cyclists, and a ‘loud’ honk for alerting oblivious drivers. LoudBicycle offers a bike horn which sounds like a car horn, and, at 125 dB, is louder than most car horns. If these options seem too expensive and you don’t mind a DIY aesthetic, consider mounting a disposable air horn on your handlebars with zip ties.
Even if you don’t have any noise making equipment on your bike, don’t be afraid to do whatever you can to get the attention of a distracted driver who you think is about to do something dangerous - yell, wave, whatever it takes. Don’t, however, let this take priority over taking whatever evasive maneuvers are available to you. Even if you’ve got the right of way and they’re clearly in the wrong you’ll still be the one who gets injured in a collision.