What type of road? Most roads are crowned, some more than others, that is why a good alignment on a car will generally have a touch(very, very small) of pull to the left to try to counterbalance this. If this happens on all roads , then what has already been said, but if it happens on only a few roads then more likely the crown. Here in our town we have a few highly crowned roads where you feel this effect, but it is mainly our "flood drainage" roads.