METHODOLOGY

The study utilized the SHRP2 NDS database that consisted of over 5.5 million trips driven by 3,542 drivers across six sites in the U.S. First, relevant events from the database were identified, and then position and kinematic data were extracted from the identified events. After that, a kinematic model of event was developed for the simulation to be able to perform risk analysis and compare potential safety benefits. Events were identified where CVT could provide a potential benefit compared to LOS systems. In total, a final set of 68 crash and near crash events were identified to carry forward in the analysis. The study calculated the minimum required deceleration to avoid a collision, the activation time difference between the systems, and the probability that at least moderate injuries would result from this crash event. A surrogate safety measure was used at each analyzed event and an injury risk model was used to predict the probability of a severe injury given the delta-v value of the subject vehicle involved in a crash.

FINDINGS

• The study found that the LOS system required an average of 2.95 m/s² higher deceleration than the CVT system to prevent potential crashes.
• Analysis of 68 events showed that the CVT system provided more than 0.25 seconds of additional reaction time in 57.4 percent of cases.
• On average, the CVT system provided an additional 0.45 seconds of notification compared to LOS regarding a potential threat.
• The results implied that three quarters (75 percent) of crashes (assuming braking only) could be avoided using LOS features whereas nine out of ten (90 percent) could be eliminated if the vehicles had CVT, which translated to a 15 percent improvement in favor of CVT.
• The study found that vehicles with CVT systems were associated with an average 26 percent reduction in the likelihood of a crash involving severe injury compared to those with LOS systems.