In Iraq, American troops no longer speed up when ambushed, trying to escape the attackers. Now, most troops have been trained, and instructed, to stop and fight, and go after the attackers. That tells you a lot about how much the situation in Iraq has changed. American troops are now better trained, and equipped (with armored trucks, UAVs and so on) than they were two years ago. There are better tactics, and combat leaders who can quickly and accurately decide if an ambush is one they should stop and fight, or run from.
Another reason for the new tactics is that the enemy would sometimes use a second ambush down the road, which blocked the road. Thus the troops would have to stop and fight anyway. Moreover, intelligence reported that the attackers often got encouraged when American troops sped away from an ambush, taking this as a victory, and as a good reason to try again. Since there were only a limited number of groups setting up these ambushes, if you stopped to fight them, and killed or captured the attackers (the usual result), there would soon be fewer ambushes in the long run. Not only would there be fewer people around to stage ambushes, because of the casualties, but the word would get around that ambushing U.S. troops was very dangerous. Intelligence also picked up information, about damaged morale among ambush gangs, after several widely publicized battles with ambushers, with many of the attackers killed or captured.
Increasingly, the improved reconnaissance tools, especially overhead UAVs streaming live video to the convoy commander, have made ambushes into opportunities to quickly turn the tables. This pays big dividends long term. The enemy sre less sure of themselves, and more likely to make mistakes or panic. In the short term, going after the ambush force yields prisoners, or dead bodies containing documents, or identities, that can help unmask another terrorist cell.
Not all convoys are stopping and fighting. Most supply convoys, and those who really have to get somewhere in a hurry, still have orders to push through an ambush, if possible. All convoys are ready to stand and fight, but only if they have to because one or more vehicles are immobilized, or the way is physically blocked.