I'm actually more active as a driver than I was at my office job. But I am prone to overeating by "grazing" on snacks throughout the day, so my main thing is to keep a running total of the calories I eat in a day. Don't forget to include beverages. Always round up if you're not sure.
By doing this, I can eat the same volume but make better choices. Or, if I feel like treating myself, I can have something calorific and compensate by cutting back for the rest of the day.
But the main thing is to be aware of how many calories everything has in it (or be able to estimate if you don't know for sure), and how much you can eat in a day before you start to gain weight. For an average healthy adult male, that's usually around 2400 kcal.
I eat station food more days than not, yet lost three stone last year.