Nighttime Driving

• Half of fatal automotive crashes at nighttime. According to the Insurance Institute for Highway Safety’s (IIHS) 2018 Fatality Facts, which summarized the United States Department of Transportation’s Fatality Analysis Reporting System (FARS) data, approximately half of all fatal crashes occurred between 6 PM and 6 AM. The National Safety Council, looking at the same dataset, found that fatal car crashes were more frequent on weekends, peaking on Saturday. They also found that during the spring and summer months, fatal crashes tended to peak between 8 PM and midnight, while from October through March, the peak for fatal crashes was between 4 PM and 8 PM. Both timeframes seasonally correlate to dusk and nighttime. Similar research by the American Automobile Association (AAA) found in a query of the FARS database that while approximately 25% of automotive travel occurs at night, half of driver fatalities and over 70% of all pedestrian deaths occur during dark driving times.

• Human vision is significantly worse at night, especially as people age. It is well-known that people simply do not see as well at night when compared to daylight hours. As the American Academy of Ophthalmology notes, night vision is mostly or completely in black and white, and color vision is poor in low light conditions. Specific problems that are common at night are difficulty in seeing distant objects, blurred vision, and glare or “halos” around lights. These problems all clearly directly affect one’s driving ability. Age-related macular degeneration is a leading cause of vision loss among older adults in the United States. Many patients with early and intermediate age-related macular degeneration do not report any problems during the daytime but may report difficulty with tasks like driving and reading at nighttime. The American Optometric Association notes these same difficulties for older drivers and warns, particularly for those 60 and over, to reduce their speed and consider limiting themselves to daytime driving.

• Degraded vision at night increases reaction time. The National Safety Council reports that, at night, “even with high-beam headlights on, visibility is limited to about 500 feet (250 feet for normal headlights), creating less time to react to something in the road, especially when driving at higher speeds.” A 2002 study of reaction times when driving at night showed that an increase in processing time occurred as contrast and luminance were decreased. It must also be noted that while movement time may be similar between day and night, it is the detection and identification stages that may be lengthened at night. Another key factor related to visibility and night driving is expectancy. Drivers can detect things in the roadway from much greater distances when an observer knows what is ahead and about where it will be encountered.

• Many automotive headlights on the road today are inadequate. Government regulations such as the Federal Motor Vehicle Safety Standards, Canada Motor Vehicle Safety Standards, and the United Nations Economic Commission for Europe specify vehicle headlamp performance. However, the low beams of many headlight systems that meet these regulations are still inadequate. AAA research found that modern headlamps on low beam may only provide adequate lighting up to speeds of roughly 40 -50 miles per hour. A 2018 IIHS Status Report found that only just over half of the model vehicles they evaluated “do an adequate job of lighting the road at night and limiting glare for oncoming drivers” and that “most good-rated headlights are optional or bundled with features that can raise the price of the vehicle … In all, IIHS engineers evaluated 424 headlight variants on 2018 models. Of these, 67 percent earn a marginal or poor rating because of inadequate visibility, excessive glare from low beams for oncoming drivers, or both.” Drivers and manufacturers must both strive to emphasize the importance of improved headlamp performance for automotive safety.

• Glare from on-coming vehicle headlights can distract drivers and reduce their visibility. While vehicle headlamps are designed to be aimed slightly away from oncoming vehicles specifically to reduce nighttime glare, the issue of glare and its effects on drivers remains. The National Highway Traffic Safety Administration (NHTSA) published a 2007 report to the United States Congress detailing nighttime glare and its effects on driving performance. They noted how glare frequently reduces the distance at which objects can be seen, increases drivers’ reaction times, increases the “recovery time” for drivers to regain their normal visibility after an oncoming vehicle has passed. These features are sometimes collectively known as “disability glare.” The phenomenon of “discomfort glare” was also described, in which drivers become annoyed and can even feel physical pain when viewing a bright light, distracting drivers from the driving task, causing them to slow down and even drift in their lane. A variety of factors contributing to glare have been identified, including varying vehicle headlamp heights, colors, size, arrangements, and aiming directions. Many organizations, including AAA, IIHS, and NHTSA, have recognized the importance of proper headlamp aiming to provide sufficient roadway lighting while limiting glare. A 2008 sensitivity analysis of headlamp parameters affecting visibility and glare also found that headlight aiming plays a critical role in both disability glare and discomfort glare. 

• High-beam headlights dramatically improve visibility at night but are woefully underused. It is well-understood that the high-beam vehicle headlamp setting provides significantly more light on a dark roadway at night, illuminating closer objects more thoroughly than low-beam headlights. High-beams also transmit light significantly farther down the road to help with the detection and identification of objects in the distance. Unfortunately, high-beam headlights are significantly underutilized. A 2008 study of nearly 100 drivers in instrumented vehicles found that low-beam headlamps were used 97.3 hours annually, while high-beam headlamps were used just 9.8 hours. However, older drivers drove far less distance at nighttime than their younger counterparts but used their high-beam headlamps far more frequently (24.2 minutes per 100 kilometers versus 4.6). This, coupled with the research on degraded vision of older drivers, suggests the importance and value of appropriate high-beam usage to improve visibility at night. One solution to increase high-beam usage at night that has gained traction is the use of adaptive-driving-beam headlights that automatically shift between low-beam and high-beam to maximize visibility for the driver while limiting glare for oncoming drivers. It should be mentioned that high-beams should not be used in certain conditions, such as when facing oncoming traffic, cresting hills, making turns, or driving in inclement weather (e.g. fog, rain, snow).

• Fatigue, alcohol, and drugs impair driving, especially at night. Drowsy driving was reportedly involved in 2.3% of the fatalities that occurred on U.S. roadways in 2015. A drowsy-driving crash was defined by NHTSA as a crash in which the driver was reported as drowsy or sleepy based on the police accident report. NHTSA further notes that it is quite likely that the rate of drowsy-driving crashes is much higher, since some jurisdictions report fatigue as an attribute of distraction and there is often a lack of firm evidence that the driver was drowsy. 2018 NHTSA data show that in the United States, 29% of all traffic fatalities involved at least one driver that had a blood alcohol concentration (BAC) of at least .08 g/dL, with approximately 75% of those crashes occurring at nighttime and nearly half occurring on weekend nights. 61% of the fatalities were the drivers with a BAC of at least .08 g/dL themselves, while 28% were other vehicle occupants and 11% were nonoccupants (e.g. pedestrians). Approximately 31% of the over 19,000 single-vehicle fatal crashes involved a driver with a BAC of at least .08 g/dL, compared to 13% of the over 32,000 multiple-vehicle fatal crashes. Men were the driver in approximately 72% of all crashes and represented 77% of the drivers with a BAC of at least .08 g/dL. Unfortunately, drivers with a BAC of at least .08 g/dL involved in fatal crashes were 4.5 times more likely to have prior convictions for driving while intoxicated than drivers with no alcohol. The 2010 estimated economic costs of alcohol-impaired crashes were $44 billion, and the estimated associated comprehensive costs were over $200 billion. Still, it should be noted that there has been steady decline in the percentage of drivers with a BAC of at least .05 g/dL since the 1970s. A 2013-2014 national roadside survey found 20% of weekend nighttime drivers tested positive for drugs, and there was a 48% increase from 2007 to 2013-2014 in weekend nighttime drivers who tested positive for delta 9 tetrahydrocannabinol (THC), the psychoactive substance in marijuana. Stimulants like cocaine and methamphetamine can make drivers more aggressive and reckless, while certain prescription and over-the-counter medications can cause drowsiness, dizziness, and other side effects that directly impair driving ability. Please also see AAAM’s position statements on fatigued driving and blood alcohol concentration for more information.

Insurance Institute for Highway Safety. “Fatality Facts 2018: Yearly snapshot.” 2019. https://www.iihs.org/topics/fatality-statistics/detail/yearly-snapshot

National Safety Council. Injury Facts: Crashes by Time of Day and Day of Week. https://injuryfacts.nsc.org/motor-vehicle/overview/crashes-by-time-of-day-and-day-of-week/

American Automobile Association. (2019). “Comparison of European and U.S. Specification Automotive Headlamp Performance.”

Goel, Ravin. Night Vision. 2018. https://www.aao.org/eye-health/anatomy/night-vision

American Optometric Association. Adult Vision: Over 60 Years of Age. www.aoa.org

Ying, G. et al. (2008). “Night Vision Symptoms and Progression of Age-related Macular Degeneration (AMD) in the Complications of AMD Prevention Trial.” Ophthalmology. 115(11): 1876-1882.

National Safety Council. The Most Dangerous Time to Drive. https://www.nsc.org/road-safety/safety-topics/night-driving

Plainis, S. & Murray, I.J. (2002). “Reaction times as an index of visual conspicuity when driving at night.” Ophthal. Physiol. Opt. 22: 409-415.

Insurance Institute for Highway Safety. (2018). “Status Report: Night Vision.”

National Highway Traffic Safety Administration. (2007). “Nighttime Glare and Driving Performance.”

Bullough J.D. et al. (2008). “Nighttime Glare and Driving Performance: Research Findings.” Report No. DOT HS 811 043.

Buonarosa, M.L., Sayer, J.R. & Flannagan, M.J. (2008). “Real-World Frequency of Use of Lighting Equipment.  Report No. UMTRI-2008-14.

National Highway Traffic Safety Administration. (2017). Traffic Safety Facts: Drowsy Driving 2015.

National Highway Traffic Safety Administration. (2019). Traffic Safety Facts: Alcohol-Impaired Driving.

National Highway Traffic Safety Administration. Drug-Impaired Driving. https://www.nhtsa.gov/risky-driving/drug-impaired-driving

Bernings, A., Compton, R. & Wochinger, K. (2015). “Results of the 2013-2014 National Roadside Survey of Alcohol and Drug Use by Drivers.” Report No. DOT HS 812 118.