Being a vehicle driver, occupant, or pedestrian on U.S. roadways has become significantly riskier. Specifically, vehicle crashes are now the leading cause of death for teenagers (ages 16-19),1 and the leading cause of injury-related deaths for elders (ages 65-74).2  Vehicle fatality risks continue to increase at an alarming rate. During 2015, more than 35,000 people died in U.S. vehicle crashes primarily due to unsafe human behaviors while driving (e.g, speeding, impairment, cell phone use).3 Through health and safety research with technology companies, transportation officials, and vehicle testing grounds, Altarum’s Center for Vehicle Safety accurately predicted that more than 37,000 people would unfortunately die in U.S. vehicle crashes in 2016. This statistically significant (>9%), year-over-year fatality increase now represents more than 100 deaths per day on U.S. roadways. While transportation officials study and debate new legislation to help make roadways safer, vehicles could be equipped with existing technologies resulting in immediate safety benefits when a vehicle crash occurs. One of these cost-effective lifesaving technologies is the seatbelt interlock.

Even though vehicle occupant seatbelt use in the U.S. is at an all-time high of 89%, approximately half of all occupant fatalities occured when seatbelts were not used (9,874 fatalities in 2015).3  Seatbelt safety studies conducted by multiple organizations, including the National Highway Traffic Safety Administration (NHTSA), have proven that wearing seatbelts reduces the risk of fatality by over 50% (45% for passenger vehicles and 60% for light trucks).4 Thus, more than 5,000 people could be saved annually by ensuring seatbelts are worn at all times, by all vehicle occupants. Seatbelt interlock devices have the engineering ability to increase seatbelt usage from 89% to full 100% compliance rates.

Current seatbelt interlock technologies work seamlessly and cost-effectively in vehicles. Seatbelt interlock technologies work to ensure that vehicle occupants (driver and passengers) are properly belted prior to the vehicle starting, or moving.  The two safest seatbelt interlock technology types include:

  1. Ignition Interlock: Allows the vehicle to start once the driver and passengers are belted.
  2. Transmission Interlock: Allows the driver to start the vehicle without being belted, and then allows the vehicle to move once occupants are belted.

A third type of seatbelt interlock technology exists and is termed a speed-limiting interlock. The speed-limiting interlock permits a vehicle to drive only at low speeds if seatbelts are not used (e.g., trucks moving materials on construction sites). While there are certain user-friendly benefits of the speed-limiting interlock, this technology does not fully safeguard vehicle occupants. Thus ignition and transmission seatbelt interlocks achieve higher levels of vehicle occupant protection and are recommended for use.

Historically, seatbelt interlock technologies have been proven as effective occupant protection devices. In 1973, NHTSA mandated interlocks to be installed on all 1974-model year vehicles. The early interlock devices were often technically flawed and frequently failed motorists attempting to start vehicles. With public and legislative outcry against the flawed seatbelt interlocks, NHTSA immediately removed the mandate in 1974.  Additionally, NHTSA shifted their occupant safety emphasis towards installing airbags that were ultimately required to be powerful enough to protect unbelted occupants. Congress then adopted a new provision as part of the Motor Vehicle and Schoolbus Safety Amendments of 1974 (Pub. L. 93-492, 88 Stat. 1470). This provision prohibited NHTSA from requiring, or permitting as a compliance option, a seatbelt interlock designed to prevent starting or operating a vehicle if an occupant was not using a seatbelt. Though this prohibition did not limit a manufacturer's right to install seatbelt interlocks into new vehicles, most perceived this and did not proceed in refining the interlock technology.

Currently, and for reasons of sales, safety, and branding, many vehicle manufacturers are now considering the voluntary installation of seatbelt interlocks. More manufacturers are now offering modernized interlock systems as standard equipment, or as optional equipment for safety-minded drivers and occupants. In fact, NHTSA has encouraged vehicle manufacturers to install seatbelt interlock systems and stated, “Voluntary implementation would likely yield important real world data about interlock systems that could be utilized by the agency in the future.”6 If consumer response towards the modernized seatbelt interlock systems is more positive, the technology could be offered more widely by vehicle manufacturers. Broad use of interlocks would reduce the total number of fatalities (and injuries) occurring in vehicle crashes and would reduce the economic losses from these deaths. The National Safety Council estimates the (real) economic loss from a single motor vehicle fatality at $1.5M, while the economic loss from a single nonfatal disabling injury at $80,700.7 Altarum’s research and analysis indicates that full adoption of seatbelt interlocks could save over 5,000 U.S. lives annually. Additionally, the U.S. economy would save more than $7.1B from economic burdens caused by these vehicle-related deaths. Altarum’s Center for Vehicle Safety continues to work collaboratively with public and private transportation safety stakeholders to help increase safety technology use and seatbelt interlock implementation. We are hopeful that interlocks will be implemented due to federal regulations, mandatory compliance by employers and fleets, or via voluntary installation by vehicle manufacturers.

If you have questions regarding seatbelt interlocks or transportation safety, please contact Marshall Contino (202-741-1536), director of Altarum Institute’s Center for Vehicle Safety.


1. Safe Kids Worldwide Press Release,

2. NHTSA, Clinician’s Guide to Assessing and Counseling Older Drivers, 3rd Edition,

3. DOT HS 812 348, December 2016, NHTSA Quick Facts 2015,

4. DOT HS 809 199, December 2000, NHTSA Technical Report,

5. NHTSA Proposed Rule, August 29th, 2013,

7. National Safety Council, Injury Fact, 2015 Edition,


Project Leader

Marshall Contino

Marshall Contino

Director of the Center for Vehicle Safety


Subject Matter Experts

Areas of Expertise