We know a Kohen can not be in the same ohel as a dead person. From what I learned, a moving vehicle does not block the tumah from coming into the car/van/plane etc. So, if one is traveling in a vehicle, he is technically sitting in one spot each time he moves (only for a millisecond, but he is stationary). The same is true for a dead body in a hearse, car or plane.
My question is, if a Kohen is about to enter a tunnel and he sees a hearse with a dead body (AND YOU KNOW THE NIFTER IS A JEW), can he enter the tunnel?