(This post originally appeared at Yahoo! Green.)

1) Going Straight in Turn-Only Lanes
When you accidentally end up in an exit or turn-only lane and still try to go straight - or vice versa - you can quickly make a lane-full of enemies. The cars behind you pile up while you stay put waiting for an opportunity to get over into the next lane. And if you're stopped at a green light, chances are good those behind you will miss their chances to turn. Horns will beep and tempers will flare. Plus, all that idling forces the cars in line to pump out even more exhaust, which means more air pollution. This situation is sometimes hard to avoid if you're lost, but for the sake of the other drivers, just make the turn instead of blocking everyone behind you.

2) Not Knowing How to Merge
Ever sit behind a driver who lets car after car pass before finally navigating onto the highway? Or maybe you've driven behind someone who slips back and forth between traffic lanes, oblivious or indifferent to oncoming cars. Whether they've neglected to use a turn signal, or they just can't pick a lane, drivers who don't merge smoothly into traffic can be blamed for some of the most common and frustrating traffic sins, including fender benders, bottle-necking and traffic jams. For tips on how to improve your merging technique, check out this helpful video.

3) Hitting the Brakes on the Highway
We're not talking about braking to avoid becoming part of the seven-car pileup ahead. But a persistently heavy foot on the brakes isn't good for your car, your gas mileage, or your fellow drivers. And if you're driving a hybrid, the stop-and-go method is just plain counterproductive. You should keep at least one car's length between you and the car in front of you when driving on highways, so if that driver slows down you have time to do the same, without stomping on the brakes. This is especially important when roads are slick from rain, ice or snow.

4) Using Cell Phones
What's worse than getting caught behind a motorist who’s driving too slowly or someone who's too busy yapping to merge correctly? Research shows that talking on your cell phone and texting are not only annoying, they're dangerous. Nearly 5,500 people died and half a million more were injured in accidents involving a distracted driver in 2009, according to the National Highway Traffic Safety Administration. So when you're behind the wheel, hang up the phone, or at least invest in a Bluetooth.

5) Cutting People Off
No one likes driving behind a motorist who cuts across four lanes of traffic to make a last-minute turn. Not only is that a recipe for an accident, but the driver who does that isn't doing his car any favors, either, since reckless driving is a sure way to wear down brake pads and the transmission. It's always wiser to turn around down the road than to cut off other drivers. You can avoid the problem by planning trips carefully before you leave. Don't blindly trust your GPS either, since a sudden recalculation could send you careening across several lanes of traffic.

6) Tailgating
Is there anything as irritating as being tailgated? Outside of someone flashing their bright lights in your rear-view mirror, probably not. And riding too closely to another car's bumper is dangerous to boot, since you increase your chances of a pileup if the car you're tailgating stops suddenly. Finally, by constantly tapping your accelerator and brakes, your car is guzzling way more gasoline than necessary. The EPA estimates that such "aggressive driving" can reduce a car's gas mileage by 33% on highways and 5% on city streets, which means keeping your cool in traffic can help you save money on gas.