ISA in the USA? The likelihood of U.S. drivers accepting and using intelligent speed assistance

June 2024

Introduction: Speeding has contributed to thousands of fatalities in the Unites States annually for decades, despite long-standing awareness of its risks. Intelligence speed assistance (ISA) is a technology designed for speed limit compliance that has been shown to reduce speeding, and European law has mandated ISA for all new vehicles sold from July 2024. The United States lags in ISA deployment, with research specific to the U.S. driving population lacking in spite of lives lost. We studied attitudes toward ISA to understand how the intervention options specified for European vehicles are associated with ISA acceptability among U.S. drivers. Method: U.S. adult drivers (N = 1,802) completed a survey that measured their agreement with statements about ISA and their driving-related attitudes and behaviors. Between-subjects assignment tied respondents to one intervention group (advisory warning, supportive accelerator pedal, or intelligent speed limiter) prior to rating ISA acceptability. Analyses estimated the likelihood of agreement that ISA would be acceptable and would be kept turned on, and agreement of the acceptability of interventions that would occur at 1–2 mph, 5 mph, or 10 mph over the speed limit. Results: About three fourths of respondents agreed ISA would reduce speeding-related crashes. Over 60% agreed that ISA with an advisory warning would be acceptable or kept turned on, whereas agreement hovered around 50% for ISA with a supportive accelerator pedal or an intelligent speed limiter. Adjusting for multiple covariates minimized the preference for advisory warnings and found a significantly higher likelihood (21% higher) that a supportive accelerator pedal would be kept turned on relative to an intelligent speed limiter. A quarter to a third of each intervention group agreed that ISA interventions at 1–2 mph over the limit would be acceptable, whereas majorities agreed ISA interventions at 10 mph would be acceptable. Conclusion: This study highlights opportunities to improve upon a modest level of agreement that ISA would be acceptable to U.S. drivers. A strong relationship between high intervention thresholds and acceptance implies there may be an ideal balance between effectiveness and acceptance. Deploying ISA in environments with vulnerable road users also has promise, given ISA's potential to reduce injury crashes and the high acceptance for its use in school zones and among urban residents. The relationship between increased fleet penetration and increased ISA acceptability suggests that U.S. driver attitudes toward the technology may adapt positively with time.