Modified vehicle lighting reduces wildlife collision risk by enhancing deer and wild pig avoidance responses at night

Worldwide, vehicle collisions with large ungulates such as deer ( Odocoileus spp.) and wild pigs ( Sus scrofa ) cause billions of dollars in damages and injure thousands of drivers, with most collisions occurring during low‐light conditions. Recent research evaluating increased frontal vehicle illumination with a rear‐facing lightbar has shown promise, but its effectiveness when paired with different headlight types remains unexplored. Furthermore, light‐emitting diode (LED) headlights have grown in popularity compared to tungsten‐halogen (halogen), yet no study has investigated their effects on free‐ranging wildlife behaviour. Compared to halogen headlights, LED headlights produce more blue light, which more closely matches the peak sensitivities of deer and wild pig photoreceptors, potentially affecting their responses. In this study, we investigated how headlight type, increased frontal vehicle illumination via a rear‐facing lightbar, and vehicle speed influenced white‐tailed deer ( Odocoileus virginianus ) and wild pig responses to an approaching vehicle using infrared videography and GPS data. We evaluated flight probability, flight initiation distance (FID) and each encounter's danger level. Over 2 years, we conducted 95 weekly nighttime drives along a 75‐km paved route in South Carolina, USA. For deer, LED headlights had no effect on their avoidance behaviour, whereas for wild pigs, LED headlights increased FIDs by 88.5 m. Lightbar illumination mitigated the effects of increased freezing and dangerously close FIDs by deer at faster vehicle speeds, when crash severity is usually highest. For wild pigs, lightbar illumination increased FIDs at faster vehicle speeds, providing drivers with more time to respond. Synthesis and applications. Generally, LED headlights had neutral or beneficial effects on wildlife responses, suggesting they could reduce collisions given the increased illumination levels they provide drivers. Additionally, our results support previous research indicating increased frontal vehicle illumination can reduce dangerous encounters with wildlife. Our findings suggest that simple modifications to vehicles, such as increased frontal vehicle illumination and the use of LED headlights, can result in large economic and driver safety benefits when scaled to the millions of wildlife–vehicle collisions that occur yearly. Read the free Plain Language Summary for this article on the journal's blog .