Like it or not, small cars are destined to become a much bigger chunk of the U.S. vehicle market.

Last summer’s soaring oil prices brought their popularity roaring back after decades in the doldrums. Now, even though fuel prices have subsided, falling incomes and tight credit have made C- and B-segment cars such as the Ford Focus, Honda Fit and Chevy Aveo the only vehicles many new car buyers can afford.

A tougher regulatory climate, with even more stringent corporate average fuel economy standards on the way, seem to ensure a U.S. product mix with a heavier dose of smallish cars for the foreseeable future. Indeed, the U.S. B-segment soon will be fattened up with the likes of the new Ford Fiesta and Nissan Cube.

A vehicle fleet richer with subcompact, minicars and even microcars, such as the tiny Daimler AG Smart Fortwo, promises numerous benefits, such as better corporate average fleet economy numbers and lower carbon-dioxide emissions. But one ugly specter sits on the horizon: the very real threat of higher rates for death and serious injury in vehicle crashes.

“We’re not trying to scare people,” says Adrian Lund, president of the Insurance Institute for Highway Safety. “But if you are in one of the smallest 4-door cars, your risk of dying in a crash is about twice as high than if you’re in the largest 4-door car.”

While a greater number of small cars actually are scoring quite well in the IIHS’s crash safety tests, which are done at higher speeds than those conducted by the National Highway Traffic Safety Admin., the organization says basic physics makes it impossible for a small, light car to offer as much protection as a bigger, heavier one.

For instance, the 1,800-lb. (816-kg) Smart Fortwo, the smallest car for sale in the U.S., actually earned the IIHS’s top rating of “good” for front and side crash protection in test results released last May.

“The big question from consumers is, ‘How safe is it?’” says Lund. “All things being equal in safety, bigger and heavier are always better. But among the smallest cars, the engineers of the Smart did their homework and designed a high level of safety into a very small package”

Numerous other smaller cars such as the Honda Fit have received “Top Safety Pick” awards from the agency, but if Lund had his druthers, consumers would opt for bigger D-segment cars with smaller engines to get the fuel-efficient ride they are looking for.

“One of the things we would like the public to understand is if they would just buy the smaller engine, a 4-door Accord can get very close to a Honda Civic or Fit in fuel economy,” Lund says. “You are giving up a lot of space to protect your family for fuel economy you could have had just with a smaller engine.”

But Lund certainly isn’t suggesting everyone go out and purchase a hulking pickup truck. The institute strongly criticized the side-impact performance of the Chevrolet Silverado, Dodge Ram and Nissan Titan in a recent spate of tests.

“These are very big, heavy vehicles that are higher off the ground. Our side-impact test should be much easier for them because the barrier interacts with the strong sill of the door. But in fact we got marginal and poor ratings,” Lund gripes. The new Ford F-150, Toyota Tundra and Honda Ridgeline all scored well on the same test during an earlier round.

Despite the concerns of the insurance industry, the demand for smaller cars from both consumers and government mandates continues to accelerate.

And even the IIHS’s own data show small cars as a whole are improving in safety. For instance, seven ’09 C-segment cars recently tested earned the organization’s highest rating for occupant protection in a frontal crash.

Models earning the insurance group’s good rating in frontal-crash tests include the Chevrolet HHR, Saturn Astra, Pontiac Vibe, Chrysler PT Cruiser, Ford Focus, Hyundai Elantra, Suzuki SX4 and Toyota Matrix. Ward’s classifies the HHR and PT Cruiser as small cross/utility vehicles, while the Vibe and Matrix share the same platform and are considered cars.

Only the SX4, Vibe and Matrix earned an additional good rating from the IIHS in side-impact crashes.

In total, 11 of the 21 current small cars tested by the institute earned good ratings in side-impact crashes, a great improvement over the ’06 model year, when just three of the 19 vehicles tested earned the highest designation.

The ’09 B-segment cars also benefitted from redesigns and showed significant improvements from the last time they were tested in 2006.

The new Honda Fit earned good ratings in front-, side- and rear-crash protection, logging big gains over the previous version that did well in front- and side-impacts but received a poor rating for rear-crash protection. The Toyota Yaris got top ratings for front- and side-impact, thanks to now-standard side airbags, but received a marginal score for rear impacts.

The redesigned Mini Cooper scored far better this time around, as well, with good front- and rear-impact ratings and acceptable side-impact. The previous-generation was rated only marginal in rear-impact protection.

The Chevrolet Aveo, Hyundai Accent and Kia Rio trailed the leaders significantly in the second round of testing, scoring acceptable rankings in front impacts but poor or marginal in side- and rear-impacts.

Standard electronic stability control also was a rarity among the small vehicles tested by the IIHS. In its latest round of C- and B-segment crashes, only the HHR, Vibe and Mini Cooper carried ESC as standard equipment. The safety feature is optional on the others, as well as the Matrix and Fit, and not available on the PT Cruiser.

Meanwhile, IIHS says the Ford Focus was the only small vehicle in the latest test to earn a good rating for its seat/head restraints in a rear crash.

“There’s no question Newton’s laws apply” to small cars, says Matt Roney, vice president, product planning at safety systems supplier TRW Automotive. Yet, he is optimistic about how much more small-car safety can be improved with the aid of passive and active technology.

The key to making small cars safer in the future sometimes involves creating a few more precious inches of crush space within the vehicle, as well as improved accident avoidance, Roney says.

Accident avoidance is crucial because a high percentage of small-car fatalities are from single-car crashes, where a vehicle rolls over or hits a stationary object. Hitting such objects is particularly dangerous for small cars.

“Cars aren’t involved in rollovers as often as SUVs and pickups, but when they do, the consequences can be deadly,” Lund says. “The smallest cars that most need this crash-avoidance feature often don’t have it.”

ESC lowers fatal rollover crash risk by 70%, the IIHS says. As a result, the feature figures prominently in its “Top Safety Pick” rankings.

“The heavier you are, the more likely you are to move another car or bend a tree a little bit; or if you hit a brick wall, break down the wall,” Lund says. Such deflection dissipates crash energy. If a car is not heavy enough to bend a tree a few inches or break down the wall, then the full force of the crash ends up going through the car – and its occupants – as a crash pulse.

Most engineers agree standard ESC is the first step in improving small-car crash avoidance by reducing the number of rollovers and preventing other avoidable mishaps simply by sensing when a rollover is imminent and braking individual wheels to bring the vehicle back under control.

However, Charlie Steffens, director-safety systems technology, TRW Automotive, says a new generation of low-cost cameras and other sensing devices is making a variety of crash-avoidance technologies available in the near future that go far beyond ESC.

Tied into electric steering and ESC, these sensing systems can provide a level of active safety unheard of before for small, inexpensive vehicles, Steffens says.

Top-of-the line luxury cars such as the Mercedes S-Class already are equipped with sophisticated radar and cameras that provide sensing for adaptive cruise control and lane-departure warnings.

But TRW is supplying a more moderately priced camera-based intelligent safety system to Fiat Auto Group for its new Lancia Delta family sedan. The system combines ESC and a lower-cost video-based lane-departure warning system with electric power steering into a system it calls “cognitive safety.”

In the Lancia Delta, TRW’s video camera technology is tied in with the electric power steering to enable haptic feedback. When the video camera detects the vehicle drifting toward the lane markings, the electric steering alerts the driver by gently tugging the steering wheel to keep the car in the lane.

That feedback could prevent a sleepy or distracted driver from leaving the road and possibly rolling over, or drifting into the oncoming lane for a head-on collision.

Another element of TRW’s cognitive-safety portfolio is a “pre-fill” feature that pressurizes the fluid in the brake pistons when it senses a collision or emergency braking situation is imminent. The feature enhances safety by maximizing braking reaction time and stopping power.

Other safety features, such as active seatbelt retractors, which have migrated from the top-of-the-line Mercedes S-Class to less-expensive models, such as the M-Class CUV, also will someday provide enhanced safety to small cars, Roney says.

Active seatbelt retractors sense when a collision or hard-braking incident is about to occur and cinch the seatbelt tighter with an electric motor so there is little slack, ensuring the driver is not out of position. If a crash does occur, seatbelt pretensioners, now standard on most new cars, activate milliseconds before the airbag inflates.

The pretensioners yank all remaining slack out of the seatbelt and pull the occupant tightly into the seat as the front airbag and knee bags inflate. This prevents drivers and passengers from “submarining” under the inflating airbag due to a loose seatbelt.

This combination of sensing, seatbelt cinching and pretensioning, combined with smarter airbags that detect exactly how fast and how hard to deploy, should make even severe crashes in small cars much more survivable, Roney insists. Blending these passive safety features with new lower-cost sensing devices that interact with a vehicle’s steering and braking all can lead to far safer small cars in the future.

Volvo Car Corp. has boldly targeted a zero fatality rate for its vehicles in 2020. If small cars in general have double that fatality rate, there will be little to complain about.

dwinter@wardsauto.com