This study estimated the effectiveness of Toyota Safety Sense (TSS) in helping prevent front-to-rear collisions among three Toyota models (Avalon, Prius, RAV4). TSS, offered as an option in model year 2016 vehicles, includes a pre-collision warning system with automatic emergency braking (AEB), in addition to lane departure alert and automatic high beam. This study addresses the hypothesis that TSS-equipped vehicles will be less likely to experience a front-to-rear crash (as the striking vehicle) compared to those not equipped with TSS.

Using Toyota-supplied production data linked to police reported crash data from 5 US states (Florida, Louisiana, Michigan, Pennsylvania, Texas) for crash years 2014-2016, the study compared crash rates (crashes per 10,000 vehicle months) of TSS equipped (n= 23,394) versus non-equipped (n= 294,931) vehicles. TSS equipment present per vehicle was identified based on VIN. This study evaluated the impact on front-to-rear crashes where the Toyota was the striking vehicle.

Exposure, using vehicle-months, was computed based on aggregate vehicle sales in the five study states for TSS equipped and non-equipped model year 2014 to 2016 vehicles. The crude rate ratio (CRR) of front-to-rear crash rates where the Toyota was the striking vehicle was calculated as the front-to-rear crash rate for TSS-equipped vehicles divided by the crash rate for non-equipped vehicles.

Given that TSS is optional, it is possible that customers who choose to purchase these safety systems also exhibit different driving and risk-taking behaviors compared to those who do not purchase the safety systems. To address a possible selection bias, sensitivity analysis examined the control outcome of front-end damage in a multi-vehicle crash, excluding the types of crashes targeted by AEB (front-to-rear).

Of the TSS-equipped vehicles, 2.46 per 10,000 vehicle-months (95%CI:​1.75-3.17 per 10,000 vehicle-months) experienced a front-to-rear crash as the striking vehicle, compared to 4.55 per 10,000 vehicle-months (95%CI:​4.37- 4.73 per 10,000 vehicle-months) of the non-equipped vehicles. Therefore, study Toyotas equipped with TSS were 46% less likely to experience a front-to-rear crash as the striking vehicle compared to non-equipped (CRR=0.54;​ 95%CI:​0.40-0.67).

The study found that when the outcome was broadened to include all vehicles with front-end damage in multi- vehicle crashes, TSS-equipped vehicles experienced 17% fewer crashes than non-equipped vehicles (CRR=0.83;​ 95%CI:​0.71-0.94) . However, no significant difference was observed if front-to-rear crashes were excluded (CRR=1.02;​ 95%CI:​0.86-1.16) suggesting that selection bias did not play a significant role in this study.

The TSS option was only available in model year 2016 vehicles, limiting the sample size and follow-up time of TSS-equipped vehicles. Future research that includes additional state data, models and model years, will increase sample sizes and may allow for estimates by model and other crash types.

In conclusion, vehicles equipped with TSS, were nearly half as likely to be the striking vehicle in a front-to-rear crash compared to non-equipped vehicles. This study contributes to the growing evidence of the effectiveness of AEB in helping prevent a significant number of front-to-rear crashes.