The worst cases are usually caused by larger vehicles. If there is an 18 wheeler accident, or a bus accident, or a train accident, the severity of the injury is likely to be higher and the need for a lawyer is greater. Attorneys often limit their areas of practice to a few specialties, but attorneys generally don't narrow the specialty into sub-specialties.

A typical car accident results in whiplash injuries, meaning neck injuries that result in severe soft tissue injury pain that tends to go away over time. In a typical 18 wheeler accident at the very least the damage to the victim's vehicle is much greater than in a typical auto accident. An 18 wheeler accident is also likely to cause severe injuries often resulting in fractures, closed head injuries, herniated disc, or death.

An auto accident is less likely to result in severe injuries. Most 18 wheeler accidents also have coverage injuries, meaning there is insurance coverage that is much greater than insurance required for auto accidents. This makes perfect sense, because the probability of severe injury or death is much greater in 18 wheeler accidents than in auto accidents.

If a law firm has 18 wheeler accident lawyers, it would probably be a personal injury lawyer. Most personal injury law firms, if not all of them, accept 18 wheeler accident injury claims. Where there is some degree of sub specialty is in the severity of the injury. There might not be an 18 wheeler accident lawyer, or a train accident lawyer, or a bus accident lawyer, or even a motorcycle lawyer, but there are law firms that limit their practice to severe injury cases. This in turn generally means that the accident law firm would only accept cases that are severe, which are generally a result of 18 wheeler accidents, train accidents, bus accidents, and motorcycle accidents.

Most severe injury claims arise from these types of accidents. Auto accidents can and do result in severe injury claims, but are less likely to result in severe injuries such as brain injury, closed head injury, herniated discs, fractured bones, or death.

The need for a lawyer also rises as the severity of the injury rises. A whiplash injury case may or may not warrant hiring an attorney. Often insurance companies refuse to pay medical bills incurred in whiplash injury cases, because the physical evidence is minor and suggests there is no injury. This leads injury victims to seek an attorney, but for the most part the fact that it is a small matter makes hiring a personal injury impractical, because there would not be a sufficient recovery to pay the medical costs and attorney fees.

Severe injury cases tend to require an attorney in most situations. An 18 wheeler accident can cause severe injury and some insurance companies attempt to seek a quick settlement and knowingly or neglectfully mislead the injury victim to believe that it is in the victim's best interest to refrain from obtaining an attorney. Once an agreement is reached the insurance company has not further risk of financial loss on the claim.

Often the injury victim is surprised to receive a bill from their health insurance company following the settlement. The bill is often equal to or greater than the settlement. Sometimes the injury victim discovers that significant medical treatment is required such as a surgery and then attempts to renegotiate with the insurance company and is quickly rebuffed. Sometimes insurance companies keep promising that a good personal injury settlement will follow and keep making the promise until there only a few weeks remaining before the statute of limitations runs out.

The victim then receives a letter advising the statute of limitations will run out in two weeks. The same personal injury settlement promises continue, until the statute of limitations runs out. Meaning the victim has lost the right to file a personal injury lawsuit, because too much time has lapse.