American armored vehicles took a real beating in Iraq, even if they were never hit by enemy fire. The heat, the sand, and the constant work wore these vehicles down. So the U.S. Army has came up with a $700,000 "reset" process that refurbished and upgraded M-1 tanks to M-1A1SA models. What the crews particularly liked about these SA (Situational Awareness) models was the many new sensors that gave the crew a better sense of what was going on outside, when all the tank hatches were shut (the vehicle was "buttoned up.")
The new goodies included the new Blue Force Tracker (BFT) gear, which reliably shows them where all friendly (BFT equipped) vehicles are at all times, on a map display. Then there is the new and improved thermal sights, that provide better images at longer ranges (exact range is secret, but said to be over two kilometers). The .50 caliber machine-gun topside gets a thermal sight. There is now a phone box mounted on the side, for the infantry to use to talk to the crew. The gunner has a GPS powered "Far Target Locate" function, which enables him to accurately locate and hit targets up to 8,000 meters away. The driver has better night vision gear, and a rear view thermal camera, making it a lot easier to back up at night, or in any weather. The commander now has periscopes and cameras which enable him to see what is going on anywhere outside the tank. This is particularly useful if the tank is taking lots of small arms fire in an urban setting, and you still have to look out for enemy troops trying to sneak up with bombs or RPGs, in the hope of getting a lucky shot.
There are a lot of upgrades and improvements in the electrical system, and other parts of the vehicle, many based on tank crew suggestions. Recently, Iraq was particularly insistent on getting the SA version of the M-1, and the 140 M-1s being built for Iraq will be M-1A1SA models. Iraqis saw the M-1 in action, and Iraqi army officers were able to hear, from M-1 crews, what the original M-1 needed to be more effective, especially in light of the Iraq experience (lots of urban combat).
The experience in Iraq has thus produced a version of the M-1 that is optimized for infantry support, which contains many elements in common with the M-1A1SA.