The finding may be especially encouraging for families of teenage drivers when newer models with the latest driver assistance technology aren’t in the budget. The same applies to business owners whose staff drive company vehicles.
“If Dad wants to pass down his old Honda Accord to his teenage daughter, adding an aftermarket collision warning system before handing over the keys is one way to give the car a safety refresh,” says Ian Reagan, a senior research scientist with IIHS and the author of the new study.
As part of an ongoing internal driver experience program, 22 IIHS and HLDI staff members signed up to have their personal vehicles outfitted with a Mobileye aftermarket collision warning system, and 17 of them also agreed to have their driving monitored by a Geotab in-vehicle telematics unit. The volunteers made their usual drives during the 12-week study period in the spring and early summer of 2017 and completed surveys about their experiences. Drivers were split into two groups: those who live in the Washington, D.C., metropolitan area near the Institute’s Arlington office, and those who live in rural and suburban Central Virginia near the Vehicle Research Center in Ruckersville.
The Mobileye (model 630) package retrofit collision warning system featured an in-vehicle display and included forward collision warning; urban forward collision warning, which operates at speeds below 20 mph; pedestrian collision warning; headway monitoring and warning, which measures following distance at speeds above 19 mph; lane departure warning; and a speed limit indicator, which displays the posted speed limit.
The crash warnings had distinct alerts that combined flashing icons in the display with audible beeps. The thresholds for triggering the various alerts were fixed. Drivers couldn’t disable or customize the alerts to their liking as is common among systems on production vehicles.
Mobileye’s aftermarket system is a passive one in that drivers still must brake or make other corrections when alerted to increase their following distance, for example.
IIHS studies show that forward collision warning and lane departure warning reduce the rates of crashes reported to police.
During a four-week baseline period, the systems were active but didn’t issue alerts. In equipped vehicles, the telematics devices logged GPS location, hard braking and cornering, travel speed and Mobileye alerts that would have been issued if the system were active.
Volunteers then drove for eight weeks when alerts were active and received weekly Mobileye “safety scores” based on rates of alerts issued per 100 miles driven within each system’s operating range. For example, lane departure warning rates were based on miles driven at speeds over 34 mph, the activation threshold.
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Among drivers with telematics, Reagan compared mean rates of forward collision warning, lane departure warning, headway monitoring and warning and urban forward collision warning during the baseline and treatment periods and between the two geographical areas. The study excluded pedestrian alerts as only one driver received one during the study period. Reagan also looked at perceived annoyance and usefulness with alerts for all drivers who had the Mobileye system.
Reagan had hypothesized that alerts per 100 miles driven would be lower during the active warning period compared with the baseline period and that the rural drivers would have lower alert rates than urban drivers due to busier D.C.-area roads, and that was the case. For drivers at both locations, forward collision warnings, lane departure warnings and headway monitoring warnings per 100 miles decreased significantly during the active warning period. Across the baseline and active warning periods, the rural group of drivers had lower mean rates of forward collision warnings, lane departure warnings and headway monitoring warnings.
As drivers got used to the system between the baseline and alert periods, the rate of forward collision alerts decreased more among the rural drivers than the urban drivers (45 percent vs. 30 percent).
The opposite was true for lane departure warning. Urban drivers saw a bigger decline in the rate of alerts than the rural drivers (70 percent vs. 54 percent) between the baseline and treatment periods.
Warnings about following too closely dropped off, too. Headway alerts fell 63 percent for rural drivers and 39 percent for urban drivers between the baseline and treatment periods.
“Volunteers showed safer driving behaviors across the study period,” Reagan says. “They used turn signals more often and increased following distances after receiving alerts. Speeding was the only thing that didn’t change much between the baseline and alert periods. Overall, only about 6 percent of miles were driven at 10 mph or higher over the speed limit.”
A 2017 IIHS study of teenagers who drove vehicles outfitted with a prototype crash avoidance system showed improved turn-signal use and lane-keeping ability but not a decline in following too closely (see “Alerts boost teen drivers’ turn-signal use,” Aug. 23, 2017).
In a post-study survey, 62 percent of the IIHS-HLDI volunteers agreed that the Mobileye system helped improve their safety while driving. Drivers assessed forward collision warning as the most useful system, followed by lane departure warning, headway monitoring and the speed limit indicator.
“When drivers perceive a system as useful, they’ll be more likely to keep it turned on and more likely to reap the associated benefits,” Reagan says. “We’ve done prior studies showing that drivers turn off collision warning systems that they find annoying or unnecessary.”
Drivers reported the most frustration with headway warning thresholds deemed too conservative. A typical complaint was receiving a warning when a vehicle cut in front of them or when changing from a slow-moving lane to a faster one — two conditions that are difficult to avoid in busy traffic.
The most frequently noted trouble spot for forward collision warning was stop-and-go traffic. Work zones and shifting lanes were trickiest for lane departure warning.
One study takeaway should be of particular interest to fleet managers who use aftermarket collision warning systems and telematics devices to monitor driving performance.
“Fleet drivers who travel congested roads would be more likely to encounter situations that trigger forward collision and headway warnings than drivers who log more miles in sparsely populated areas,” Reagan notes. “Their managers should take into account external factors such as traffic density when comparing drivers on safety measures across geographical regions.”
Earlier in The BRAKE Report: Mobileye reports deal to equip 8 million vehicles