"Another problem is that the US troops tend to have two-stage checkpoints. First there's a knot of Iraqi security forces standing by a sign that says, in Arabic and English, "Stop or you will be shot." Most of the time, the Iraqis will casually wave you through.
"Your driver, who slowed down for the checkpoint, will accelerate to resume his normal speed. What he doesn't realize is that there's another, American checkpoint several hundred yards past the Iraqi checkpoint, and he's speeding toward it. Sometimes, he may even think that being waved through the first checkpoint means he's exempt from the second one (especially if he's not familiar with American checkpoint routines).
"I remember one terrifying day when my Iraqi driver did just that. We got to a checkpoint manned by Iraqi troops. Chatting and smoking, they waved us through without a glance.
"Relieved, he stomped down on the gas pedal, and we zoomed up to about 50 miles per hour before I saw the second checkpoint up ahead. I screamed at him to stop, my translator screamed, and the American soldiers up ahead looked as if they were getting ready to start shooting."
"Fear of insurgents and kidnappers are another reason for accelerating, and in that scenario, speeding up and getting away could save your life. Many Iraqis know somebody who's been shot at on the road, and a lot of people survived only because they stepped on the gas.
"This fear comes into play at checkpoints because US troops are often accompanied by a cordon of Iraqi security forces - and a lot of the assassinations and kidnappings have been carried out by Iraqi security forces or people dressed in their uniforms. Often the Iraqi security forces are the first troops visible at checkpoints. If they are angry-looking and you hear shots being fired, it becomes easier to misread the situation and put the pedal to the metal."
It reminds me of the P. J. O'Rourke piece where he writes that there are two kinds of roadblock: one where you must stop, or they shoot you, and the other where you must not stop, or they shoot you. How do you tell the difference? You don't!