How much light is too much light?

Intense headlamps and brighter interiors can make driving safer, but can also dazzle and confuse – a problem that researchers are working hard to solve

Mar 29, 2008

Special to the Star

As vehicles become faster and quicker, their drivers need to see farther and more clearly down the road they're travelling at night.

Inside the vehicle, meanwhile, subtle interior lighting is important to illuminate the controls and amenities, but not so brightly that it affects the driver's night vision.

It's one thing to turn night into day, and quite another to dazzle yourself and other drivers.

How much light is enough these days, and how much is too much?

Depth perception, colour recognition and peripheral vision all diminish as the sun goes down, which directly affects safety. According to the National Safety Council in the U.S., traffic death rates are three times higher at night than during the day.

To try to counteract the potential dangers, modern headlights throw their light farther down the dark end of the street. The brightest are High Intensity Discharge headlights, available on many new vehicles.

Compared to the more traditional halogen bulb units, which have been around since the 1970s, HIDs (also called Xenons) emit a bluish-white light that is two to three times as bright as halogen. This extra light also fills in the gaps at the outer edges of the beam pattern that halogens miss.

Initially, HIDs were considered a novelty – more of a distraction than an aid – because of their blue-white glow. The perception was they caused more glare to oncoming drivers. But research by Michael Flannagan, a professor at the University of Michigan's Transportation Research Institute, shows that HIDs actually cause 25 per cent less glare than halogens.

A different approach to nighttime driving safety are the new "intelligent lighting" systems currently in development with Audi, BMW and Mercedes-Benz that's linked into a vehicle's GPS system. Marcin Gorzkowski, senior regulatory development engineer for Transport Canada Road Safety, thinks these systems scould be the next big thing.

Dubbed Adaptive Forward Illuminations Systems, in essence, headlights adapt to a vehicle's speed and path.

Some production cars already have a version of this. If the car turns, the lights turn. Slow down, and the lights reduce to better illuminate the area in front of vehicle. Speed up, the lights project farther down the road.

The GPS-based technology goes a step further and anticipates the road ahead. Approach a curve and it turns the beam; approach a town and the brights dip. But this technology is still a long way off realization.

Some expensive cars already in production even offer a "night vision" option, similar to that used in military night-vision glasses.

Mercedes-Benz has it as a $2,500 option in its CL- and S-class cars, in which infrared lamps scan the road ahead, and project a black-and-white image of it onto a small portion of the instrument panel below the driver's line of vision.

Cadillac offered similar NightVision technology on its deVille, but the option never caught on among buyers and it was dropped in 2005.

Illumination inside the vehicle is just as important, and potentially even more distracting, than what's to be seen outside.

Your family's Ford Taurus station wagon in the 1980s likely had a couple of light sources inside – maybe a small bulb to light up the driver's instrumentation and the radio. These days, some modern vehicles have interiors that resemble video arcades. Combine their glowing bulbs with the lack of light outside and it can be exhausting on the eyes.

But according to Ralph Gilles, vice-president of design for Chrysler's Jeep and Truck division, newer LED lighting is now available that provides a crisper, more even light than conventional incandescent lights.

"(LEDs) are used now more than ever for soft, full-time interior lighting over centre consoles," he says.

"We use this in six seating locations in the Town & Country and Caravan. This allows drivers to still find objects inside the car while avoiding turning on the harsh white dome light which can be hazardous while driving at night."

There is still debate as to whether one colour of light is more legible than another.

"White is still the undisputed legibility king but red, blue and greens can be used successfully as long as the contrast is appropriate.

Darker colours like purple, violet and dark blues are better used as accents than for information distribution."

At the very least, Flannagan, at the University of Michigan, says drivers should take the time to adjust the lighting in their cars as low as possible so their vision doesn't have to work harder to adjust to the lesser light outside.

After all, aircraft passenger cabins are dimmed on take-off and landing in case there's an incident and the cabin needs to be evacuated quickly. A dim cabin allows the passengers to adapt more quickly and see better in the darkness outside.

Transport Canada's Gorzkowski would also like to see the design and placement of interior controls and graphic symbols harmonized around the world, regardless of the country.

"This way, drivers can become familiar with the controls faster when travelling or renting vehicles," he says.

Regardless of the types of night vision aids you use or how attentive you are as a driver, you can't control the amount of light available on the road – whether it's the harsh glare of a streetlight in a new subdivision or the gloom of a rural highway.

To determine where or how many street lights get installed, most cities adhere to the Illuminating Engineering Society of North America lighting design standards, says Scott Edey, program manager for the City of Ottawa's street and community lighting.

The amount of street lighting is also determined by the city's database of daily traffic flow and if the location is near schools, hospitals, parks or seniors' residences.

Cities in North America, including Toronto, are also looking into new Light Emitting Diode street lights.

It promises to be more energy efficient, last almost four times longer and have cheaper maintenance costs than the high-pressure sodium street lights that are still the most commonly used.

There will always be a push to make things safer for drivers, passengers and pedestrians – even if it means turning night into day.

Toronto Star