Low Speed Crashes Pose Significant Injury Risk

An important new study in the International Journal of Environmental Research and Public Health shows that conventional thinking may be wrong. Motor-vehicle accidents at low speed or with low property damage have a strong risk of injury. This has important medical-legal implications, but moreover, it has personal implications for many Australians. There is a tendency for people to under-respond to low-speed, car-crash injuries. It’s normal to think, “There can’t have been a serious injury from such a small crash.” Now, we understand that the forces in low-speed car crashes can be quite injurious, and people who feel injured should seek treatment.

For decades, insurance claims supervisors have refuted injury determinations with biomechanical arguments. The refusal to recognize the crash injury starts with older studies measuring the acceleration of activities of daily living (ADLs) such as sneezing, flopping into a chair, or stepping off a curb. Then they associate those accelerations with the accelerations experienced by passengers in low-speed crashes. Sometimes, the argument will also use car damage as a proxy for speed. In bumper-to-bumper collisions, significant car damage is unusual under 13 kph.² The argument holds that since these activities of daily living are non-injurious, car accidents with similar acceleration must be non-injurious as well. However, the underlying premise there is an unproven theory. The premise is that acceleration alone can be a proxy for injury risk. Nolet et al. evaluated that premise and found it to be “scientifically invalid.”

Previous literature made assumptions about the head acceleration in low-speed crashes. In actual crash-test data, head acceleration was roughly 13 times greater than head acceleration measured in ADLs. Impact duration was roughly 70 times longer in crash pulses compared to ADL pulses. Based on biometric data, the authors conservatively calculate that the risk of injury in a low-speed collision is at least 2,000 times greater than the risk of injury from ADLs such as sitting. Low-speed / low-damage auto accidents are not comparable to ADLs in terms of head acceleration, impact duration, or risk of injury.

This observation is supported by the epidemiological data. Injury rates from minimal and no-damage crashes have been measured at greater than 20%.³ Similarly, risk of injury has been measured at 12% for speeds of less than 8 kph and at 47% at 11 kph.^4,5   

If you may have experienced musculoskeletal injury from a motor-vehicle accident, remember Advanced Physiotherapy. We work with motor-vehicle injuries and bill the insurer directly, with no out-of-pocket expenses for our patients. Please call Advanced Physiotherapy and Injury Prevention at (02) 4954 5330.

References

1. Nolet PS, Nordhoff L, Kristman VL, Croft AC, Zeegers MP, Freeman MD. Is acceleration a valid proxy for injury risk in minimal damage traffic crashes? A comparative review of volunteer, ADL and real-world studies. International Journal of Environmental Research and Public Health. 2021 Jan;18(6):2901.
2. Bailey MN, Wong BC, Lawrence JM. Data and methods for estimating the severity of minor impacts. SAE Transactions. 1995 Jan 1:639-75.
3. Freeman MD, Leith WM. Estimating the number of traffic crash-related cervical spine injuries in the United States; An analysis and comparison of national crash and hospital data. Accident Analysis & Prevention. 2020 Jul 1;142:105571.
4. Cormier J, Gwin L, Reinhart L, Wood R, Bain C. A comprehensive review of low-speed rear impact volunteer studies and a comparison to real-world outcomes. Spine. 2018 Sep 15;43(18):1250.
5. Freeman MD. Biomechanical, mechanical, and epidemiologic characteristics of low speed rear impact collisions. In Proceedings of the 67th Annual Meeting of the American Academy of Forensic Sciences 2015 Feb (pp. 517-518). Colorado Springs, CO: American Academy of Forensic Sciences.