My son likes any machine with wheels and makes a head turning sound. It doesn't matter if its a truck, car, motorcycle, tractor or airplane, he likes to point and says vroom vroom.
At times, we could be playing in the backyard, running, climbing or laughing really hard and if he hears a motorcycle somewhere off in the distance, he stops, make his sound and points in the direction of the sound.
When we are shopping, Jeff takes him down the "boy" isle (even though its not limited to boys) to see what there are for vehicles. Of course we all have to push the buttons on all the kid trucks or what every there is around, but then Drew finds that one thing he wants (or really what Jeff wants to get him). Drew has his own set of motorcycles, a Ford Pick-Up truck, lots of match box cars, and equipment trucks. Drew is in his glory and carrys around a certain vehicle from day-to-day. There are vehicles spread all over the house.
Drew also just doesn't have the physical vehicles, he has two truck books, a tractor book and a train book he reads often. These are in the mix of his favorite books and we read them often.
I can't wait until he can get outside to help out his Daddy, Grandpa Charlie and Grandpy with working on the cars. Drew already wants to help with everything that is done, I can imagine when he's old enough to have his own tool box to fix the cars.