Building on what they learned in Iraq, American troops in Afghanistan are relying more on foot patrols to avoid IEDs (Improvised Explosive Device, usually mines, booby traps and roadside bombs). There are few roads in Afghanistan, and most of them are unpaved. That makes it easier to plant roadside bombs. But by using foot patrols more often, the IED tactics become much less effective. Currently, about 60 percent of NATO casualties are to IEDs, almost all of them used against vehicles.
Infantry on foot must still be alert to the possibility of IEDs. The enemy knows they have little chance of success in a shoot out with Americans, and thus prefer to try hitting U.S. troops via what amounts to a remote ambush. While this tactic has a low probability of success, it's more certain, and a lot safer, than a firefight. Troops on foot patrol are still in danger of IED casualties, usually when they repeatedly patrol along the same route, or when one of their waypoints becomes known. The terrorists have bomb planting teams that can work quickly to emplace and camouflage an IED.
While air cover (a helicopter or UAV), is often assigned for convoys, foot patrols rarely get it, unless there is a high probability that hostile forces would be in the area. Even then, it's not a sure thing that the UAV will catch the enemy planting the IED. The enemy will sometimes plant several IEDs at places where patrols might pass. If the enemy has enough resources to plant a lot of IEDs, and risk losing most of them (as is usually the case, because most are spotted and destroyed by U.S. troops), or just gets lucky, they will be able to set an IED off close to a foot patrol. Since these IEDs often use large explosives (a barrel filled ammonium nitrate fertilizer and fuel oil), the effect is the same as using heavy artillery on the troops. Infantry in the open (standing up) are very vulnerable to this kind of attack. If in an area with these determined IED builders, patrols can carry a portable electronic jammer, which will either neutralize the IED detonating system, or force the bombers to use wires, which are easier to detect.
The foot patrols also enable the troops to maintain closer contact with local civilians. Even in southern Afghanistan, the Taliban is hated by most of the population. Thus the foreign troops are appreciated, because they cannot be bribed, and will always defeat the Taliban in a gun fight. Developing a relationship with the locals often leads to tips about where IEDs are planted, and who is planting them.