Opening door to traffic

This would (should?) be the No. 1 mistake on any list of this nature. Drivers opening their doors into the flow of traffic is the biggest danger to bikers. It creates a situation where a possible oncoming biker that is right next to the car has to decide between slamming into the door or swerving into traffic without knowing if another vehicle is there that will hit them.



Passing too close to bikers

State law requires that cars pass bikers with at least 3 feet of clearance separating the two, but that seldom happens. Sometimes, cars pass close to bikers to intimidate them or if the driver thinks the biker is taking up too much room. This is dangerous for many reasons, the biggest being that all it takes is a small pothole, rock or buckled pavement to knock a rider a bit off track. If there is no safe space to move into, bikers will collide with cars.



Turning right in front of bikers

Since bikers are required to travel at the right side of the road, they oftentimes are in the blind spot to drivers turning right. When that happens, the cars might just turn into bikers who are in the established bike lane.



Occupying an unprotected bike lane

Bikers have to travel as far right of the lane as safety permits, according to law. When you've got your car double-parked there or a taxi is idling there waiting for a fare, it forces cyclists to travel in the lane of moving traffic. That's not good.



Not using a turn signal

No-brainer, right? Everyone has this complaint about other drivers, but it can be very hazardous for bikers. Let's say a biker is in the bike lane where he's supposed to. All of a sudden, you brake. The biker thinks nothing of it, since he's in the bike lane. But—surprise!—you've decided to turn right, which is right in his line of travel. See the problem?



Running red lights

No explanation needed.



Yelling at bikers

Drivers—or car passengers—who think bikers have wronged them on the streets sometimes use their open window to interact with said cyclists, but that's not advised. First, it distracts the driver of the car. Second, it distracts the cyclist. Third, if things escalate, nothing good can come of it. If you really need to express yourself, just proudly display your middle finger with a big smile on your face and move along.



(True story: A driver once yelled at me while I was riding in the rain: "It's raining, asshole." Really, what's the point of that, douchebag?)



Honking unnecessarily

Honking just because you don't like to drive slowly behind a biker or because of some other terrible reason is pointless. It might make you feel better, but it interrupts the concentration of a biker, and it might even startle them into making a riding mistake. If you honk, make sure it's for a legitimate reason, otherwise bikers will be trying to figure out what's going on.



Splashing riders

Drivers know exactly what they're doing when they speed through huge pools of water on the street as they pass by a biker in the rain. It's rude and it's dangerous. A wave of water can knock a rider off course, not to mention temporarily blinding them until they can wipe the water from their goggles, glasses or face.



Expecting bikers to run red lights, stop signs

I can't tell you how many times I've stopped at a stop light or stop sign and had a driver wave me through even though it's clearly not my turn to go. If I do that, I can't be sure other drivers expect me to head into the intersection. Just follow the rules of the road and everything will work out just fine.