Consumer Reports' latest examination of vehicle blind zones -- the area behind a car or truck that's hidden from the driver's view -- shows that the 2006 Jeep Commander Limited ranks as the worst vehicle overall.

CR measured the blind zone behind the Commander at 44 feet for a driver who is five feet, eight inches tall and a stunning 69 feet for a shorter driver (five feet, one inch tall) with all three rows of seats raised. The Commander's blind zone is considerably larger than that for other midsized and large sport-utility vehicles (SUVs).

Until now, the vehicle with the worst blind zone in Consumer Reports' tests was the 2002 Chevrolet Avalanche 1500, a pickup truck, which had a blind zone of 29 feet for a five-foot, eight-inch driver and 51 feet for a five-foot, one-inch driver.

But the redesigned, 2007 Chevrolet Avalanche LT has no blind zone when equipped with the optional rearview camera. Without the camera, the vehicle had a 31-foot blind zone for a five-foot, eight-inch driver and 50 feet for a short driver.

The Commander also offers an optional rearview camera, which CR's test vehicle lacked. This camera can significantly reduce or eliminate the blind zone.

To help consumers understand how large some blind zones are, Consumer Reports has been measuring the blind zones on vehicles that it tests and rates since 2003. CR's database now covers about 200 vehicles from model years 2002 through 2007.

To measure the blind zones, a 28-inch traffic cone was positioned behind the vehicle at the point where the driver could just see the top. This cone simulates the height of a small child.

"Consumer Reports findings illustrate that the danger of vehicle blind zones correlates with the use of large SUVs, minivans and pickups trucks as common family vehicles. Consumers must be cognizant of this danger-and the value of rearview cameras-when going out to purchase a new vehicle," said Don Mays, senior director for product safety and consumer science at Consumer Reports.

Kids and Cars, the safety group, estimates that more than 100 children were killed by vehicles whose drivers simply could not see them in the blind zone behind the vehicle. According to the Centers for Disease Control and Prevention in Atlanta, nearly 7,500 children were treated in United States emergency rooms between 2001 and 2003 for backover injuries.

Many of these incidents could have been prevented if drivers had a way to see or detect what is behind them while backing up. Every vehicle has blind zones. Side and rearview mirrors are insufficient to combat them. Consumer Reports tests show that, in general, the longer and higher the vehicle, the bigger the blind zone is likely to be.

There are no federal government requirements for backup warning sensors or rearview cameras on any passenger vehicle sold in the United States

"Unfortunately, the few vehicles that now come with this technology are higher-end models, and most devices are available as an extra-cost option -- often requiring the purchase of other equipment like an expensive navigation system," said Sally Greenberg, senior product safety counsel for Consumers Union in Washington, D.C.

"We believe that backup technologies, such as rearview cameras are essential, and should be a requirement by federal law. Their cost is small compared to the cost of a child's life. And once this technology becomes standard equipment in vehicles, systems will become more economical for manufacturers to produce," she added.

"Without these devices, parents and families will continue to suffer the terrible tragedy of accidentally backing over a child," Greenberg said. "That is why it is critical that Congress pass the Cameron Gulbransen Kids and Cars Safety Act of 2005-to require a rearward visibility standard that will provide drivers with a means of detecting a child behind the vehicle."

Consumers who wish to improve the safety of their current vehicle can add an aftermarket rearview camera. Consumer Reports tests have shown that most work well. Such cameras typically cost several hundred dollars and are best installed by a professional.