Ram 2500 Overheating

I have a 2002 Dodge Ram 2500 with the 5.9 cummins engine. Only in heavy traffic the engine tends to overheat.

I have the 01 diesel, and something that you might check, to see if you have it, is a crankcase breather bottle on the front engine cover. If you have that, then take a look down between your rad and charge air cooler. You might find that the rad is coated in dirt and dust. This is from the crankcase vapors escaping from that bottle, and coating the rad.
I had this problem on the 01, it started overheating all the time, took a look at it, and there it was. I used to clean that bottle out every 1000 km, but it still was not enough, so now, for summer, i run a straight crankcase vent tube, old style, and in winter I put the bottle back on, as it helps to keep the breather tube from freezing in colder weather.

Good luck