When you think of standard types of assault charges, they usually come from some deliberate action being taken on the part of the person who is being charged. This could be a violent physical action, a threat, the use of intimidation or something of this nature. While it may happen in the heat of the moment, it is still usually intentional.
The same is not always true for vehicular assault charges, and it could even be argued that these happen more often due to recklessness or negligence than for any other reason.
Under New York state law, for example, vehicular assault in the second degree could be used if you are involved in an accident that causes serious injuries to another party while you are under the influence of drugs or alcohol. These charges could then go on top of additional charges simply for violating the laws regarding the use of a motor vehicle while being influenced by these substances.
These charges can also be used depending on the types of commodity being transported by the vehicle. For example, if a serious injury is caused by a driver who is carrying flammable gas, explosives, radioactive materials, and other things of this nature, vehicular assault charges could be leveled.
Naturally, they are not going to be used in every single case in which an accident leads to injury, but the law leaves the door open to use significant charges when the criteria are met.
If you're facing charges of this type, it's wise to know exactly what the law allows and the legal options that you have.
Source: FindLaw, "N.Y. PEN. LAW § 120.03 : NY Code - Section 120.03: Vehicular assault in the second degree," accessed July 03, 2015