There's good news for automakers this summer: Domestic sales of cars and trucks were up almost 15 per cent in July, and are on track to reach 11.8 million units by the end of the year.

The biggest gains came in the truck and luxury SUV segments. But some trucks and truck-based SUVs still posted declines in sales for the month, including the Chevrolet Colorado and Hummer H3.

Why didn't they do as well as the rest of the segment? Perhaps because they have some of the lowest safety scores in their class -- making them among the most dangerous new trucks on the road.

Behind the Numbers

The list of the year's most dangerous trucks is based on Insurance Institute for Highway Safety crash-test results for 2010 model-year pick-ups. (Truck-based SUVs were also included.)

After each crash, dummies are checked for trauma in 28 body regions for front crashes, and 37 regions for side crashes. Ratings for each region are based on specific parameters: For instance, a "poor" rating means severe and possibly fatal trauma happened to drivers and/or passengers during the crash; a "good" rating means little to no trauma occurred.

Each truck earned a value for overall front, side and rear ratings, with more points awarded for better results ("good" received 4 points, "acceptable" received 3 points, etc.), for a maximum possible total of 12 points. The vehicles on our list scored the lowest number of total points of all trucks. We broke ties by docking points according to occupant trauma ratings within each category (front, side and rear impacts).

Danger is relative

It's important to note that all of the trucks on our list exceed federal safety standards, and they're all safer than cars manufactured just a decade ago: They are the "Most Dangerous" only in the context of similar new models. Some models on our list earned the lowest scores in their class, but still scored as many as 10 points out of 12, including Nissan's Titan truck. The $26,540 Titan had scores only slightly lower than others, in otherwise overwhelmingly safe classes.

Furthermore, IIHS tests are more severe than those administered by the National Highway Traffic Safety Administration. Its front test is a 40-mile-an-hour front-offset collision into an unmoving barrier; its side crash is a T-bone collision set at 30 mph. NHTSA tests head-on collisions using a concrete barrier that strikes at 35 mph, and its researchers evaluate fewer sections on the dummy's head, chest and legs. Side impacts are recreated at NHTSA using a 1.5-ton trolley set at 38 mph.

Automakers respond

The manufacturers of the cars on our list are quick to point out their car's relative safety. "All GM vehicles meet or exceed government safety standards," said GM in a statement. "GM conducts well over 100 safety tests on every model to balance safety performance before, during and thanks to OnStar automatic crash notification, after a crash."

"Chrysler, Jeep, Dodge and Ram vehicles meet or exceed all applicable Federal Safety standards. No single test can determine a vehicle's overall safety performance," said Chrysler, in a statement. "Our priority continues to be designing vehicles that perform safely for our customers and their families in everyday driving conditions."

"Nissan takes its commitment to product safety and customer satisfaction very seriously," said a Nissan statement. "All Nissan and Infiniti vehicles are designed and engineered to meet or surpass government safety regulations as well as our own rigorous internal safety requirements."

Detroit does well

Domestic trucks like the $16,985 GMC Canyon dominated our list, but don't let that fool you. American automakers produce more than 80 per cent of the trucks on the market today, and most of those are very good. Ford's F-150, for instance, received top honors in IIHS's front-side and rear crashes. And the GMC Acadia, Buick Enclave, and Chevrolet Traverse -- all large SUVs made by American companies -- received stellar safety scores in the same criteria.

Big trucks tend to lag behind in safety ratings in part because they're usually redesigned every seven years or so, less often than big-selling sedans, so it takes longer for safety improvements to be implemented into new vehicles. With cars, which sell more frequently and at bigger profits, the motivation for automakers to adjust safety equipment is much stronger.

Mid-sized is safer

David Zuby, the senior vice president of vehicle research at IIHS, says his organization recommends mid-sized sedans to drivers concerned with buying the safest vehicle they can afford. The middle size generally affords better gas mileage than an SUV, which wins in a crash determined by pure physics -- but it still maintains a size advantage over compact sedans and coupes on the road.

Crossovers and wagons fall into the "recommended" category as well, Zuby says. Trucks and SUVs, on the other hand, do offer a lot of mass, but are prone to problems that comparably rare in other vehicles.

"What you have to be aware of when you're considering an SUV or a pick-up truck is the fact that those vehicles are more prone to roll over," says Zuby. "And a rollover is a particularly dangerous type of crash."