Agreed. Check the fan. Modern cars have an electrically-driven fan instead of the belt-driven ones of the old days. They only come on when a temperature sensor reaches a certain point. Usually, the fan will only come on when the car is idling or in stop-and-go traffic. Open-road driving usually provides adequate airflow to keep the coolant temperature in the normal range. So, if the car is overheating in traffic but not on the highway it's probably a fan problem. If it's overheating on the highway too, get a can of radiator flush, flush the radiator and replace the coolant. If that doesn't do it, check the radiator hoses. Sometimes an old hose will delaminate and form an internal bubble that will constrict coolant flow. If that's not the problem you may have to have the radiator physically cleaned at a radiator repair shop.

Bruce