Dangers await in the dark hours

For motorists with poor night vision, driving on a busy freeway in the evening can be as disorienting as hurtling through the flashing lights and darkness of Disneyland’s Space Mountain.

Believe me, I know: I’ve struggled with night vision problems for years. I’ve had many a harrowing drive along the 405 Freeway at night -- missing exits and misjudging distances. Even on some surface streets, detecting lane lines and navigating around concrete dividers can be tough.

Night driving is more challenging and dangerous than many people realize, says James Solomon of the National Safety Council. Traffic death rates are three times greater at night, according to the nonprofit group.

Not all night fatalities can be blamed completely on poor visibility. But night driving is fraught with problems that can make it more hazardous than daytime driving, according to safety experts.

“There’s myriad factors that can be involved,” says Solomon. Glaring headlights, vehicles speeding by, poor depth perception and fatigue can contribute to night-vision problems, he says.

Ninety percent of a motorist’s reaction depends on good vision, according to the safety council. Since vision is limited in darkness, such things as depth perception, peripheral vision and color contrast are compromised.

The National Highway Traffic Safety Administration is researching ways to improve nighttime driving safety, citing concern over the number of fatal accidents at night.

Mike Flannagan at the University of Michigan’s Transportation Research Institute estimates that 2,300 pedestrians a year are killed in nighttime accidents. Pedestrians are particularly at risk if they are under the influence of alcohol or walking on high-speed, limited-access roadways, he says.

Difficulty driving at night is not just the result of someone’s poor vision or age, says Solomon. Even a young motorist with good vision may have problems with glaring headlights. How long it takes to recover from excessive glare depends on the individual. For some, bright headlights can leave them temporarily blinded. Lane lines and worn or nonreflective signs can also confuse motorists in the dark.

Los Alamitos optometrist Sharon Yamanaka comes across patients as young as 20 with night-vision problems. “They have a hard time judging where the lane lines are,” she says.

On freeways, “they have a hard time seeing signs and exiting off the freeway ramps. They find their clarity is not that good at night.” Yamanaka often hears complaints in the fall when it gets dark earlier in the day.

Some of her patients simply avoid driving at night. Others find some improvement with an adjustment to their eyeglass prescriptions, she says.

The traffic safety administration warns that cataracts, which cloud the eye’s lens, make night vision worse, intensify headlight glare and lead to double vision.

Dr. Raphael C. Caruso of the National Eye Institute in Bethesda, Maryland, says vehicle speed plays an important role in night-vision driving impairment.

“With an increase in speed, the available time to react appropriately to a visual stimulus decreases,” he says. As with any other condition that impairs a driver’s ability to perceive and react, safety is reduced, he says.

When a vehicle is speeding along a freeway, for example, the driver is taking in a lot of data through peripheral vision, says Solomon. “But the brain can only absorb so much information.” At some point, the driver develops tunnel vision and is only able to look straight ahead, ignoring what’s occurring to the left or right.

This tunnel vision or side blindness accounts for the high number of crashes at night, Solomon says. Add alcohol or drugs and the risk is even greater.

To improve night-vision driving, some automakers have already introduced new technologies. Others are scrambling to find additional new ways to prevent nighttime accidents.

Next week: A look at how well night-vision devices work.

Jeanne Wright can be reached at jeanrite@aol.com.