CNET's tech tests for cars

CNET and car reviews may appear to be an unlikely combination, but new cars have become technology platforms, using electronics to inform and entertain drivers, avoid collisions, and even save fuel.

Since we began reviewing cars in 2004, automakers have increasingly included navigation, Bluetooth phone systems, and advanced technologies for playing digital music files in dashboards. In fact, the latest trend is to give cars complete data connections, letting drivers use online search to find destinations or listen to streamed music from an Internet-based service.

Given our technology focus, CNET reviews cars differently than traditional publications such as Car and Driver, Road & Track, or Consumer Reports. Though the instrumented performance testing conducted by other publications certainly remains valuable, we spend as much time testing a car's cabin technology as we do its driving character. We want to see if the voice command is useful, or how well the navigation system guides you to a destination, or whether a blind-spot monitor provides a visible-enough warning.

Read CNET's tech car buying guide to see what's important in new car technology.

Rating
We break our rating system for cars into three main areas: cabin technology, performance technology, and design. The heaviest weighting goes to the first two categories.

Cabin technology includes dashboard electronics, primarily navigation, phone, and audio, along with driver assistance features. More recently, we added connectivity, which covers any features powered by external data, as a subcategory of cabin tech. Voice command also figures into cabin tech.

Performance technology covers engine, transmission, steering, and suspension. While power is nice, we also look at fuel efficiency, particularly technology that enhances efficiency. We also look at how technology benefits standard systems like electric power steering, suspension, and all-wheel-drive systems.

Design encompasses the look and general practicality of a car, and also the usability of its cabin tech interface. For example, is its touch-screen interface attractive and functional? As for the body, does it give the car a distinct look, and does it reflect the automaker's design language? Just because a car looks different from the norm does not automatically make it ugly, so we rarely mark down a car if its designer tried something new. And being bland will not earn a car any extra points.

Shakedown cruise
When we borrow a new car for review, our first task it to pair a phone with its Bluetooth phone system. We check out all of the related features, such as if the car makes the phone's contact list available on its LCD or through voice command. We also begin by setting up any app connectivity feature that relies on a smartphone.

With the phone paired, we take a shakedown cruise of about an hour. While the car is still parked, we enter a destination into the navigation system, if the car has one. We look at the various destination options, such as points of interest, search, and address entry, then enter a destination using the touch screen.

This process gives us an initial read on touch-screen response and route calculation speed. We can preview the route to see if it looks efficient, compared with our local knowledge of the streets and highways around the San Francisco Bay Area. Likewise, we can usually see if the system takes traffic into account for its route calculation.

On this initial drive, we listen to the navigation system's voice prompts to see if it uses text-to-speech to say street names, and look for visual turn graphics on the LCD and instrument cluster. We'll also deviate from the navigation system's route to see how well it copes with on-the-fly route recalculation and see how well the map keeps up with the car's location.

Between turns, we attempt a hands-free phone call, usually to a voice mail number back at the office, which lets us evaluate the audio quality of the call. Making a call also tests how well the voice command system can understand our speech.

By this point, we've usually hooked up a digital-music device, such as an iPod, USB drive, or Bluetooth streaming audio, to the car's stereo. We check how many audio sources are available, take a look at the song selection interface, and listen to the stereo quality. Setting the tone controls to flat levels lets us hear the factory default music reproduction.

Finally, we also begin to get a sense of what the car feels like to drive. With the car set for normal driving, leaving all sport or "eco" settings off, we feel for accelerator and steering response. How powerful does the engine feel? If it is a manual transmission, how easily does it shift? How well does the car ride?

We often go into this shakedown cruise cold, without knowing horsepower or torque numbers, and sometimes not even checking the engine type or how many gears are in the transmission. Coming in without going over a spec or feature list lets us discover things such as rearview cameras and blind-spot monitors. Looking around a cabin, we occasionally find it necessary to ask, "What does this button do?"

Extended seat time
After our shakedown cruise, typically we go for two additional drives of 3 to 6 hours each (we drive cars for a minimum of 200 miles). By these subsequent drives, we've read over the automaker's literature and evaluated any important tech features.

Spending hours in the driver's seat, we use voice commands to set destinations into navigation, use the car's interface to select music while giving the audio system a workout with a wide variety of music, and perform any further testing of the phone system deemed necessary. While the first drive lets us discover which features a car has, more drives let us see how well these features work in different environments, from speeding down a freeway at 65 mph to creeping from stoplight to stoplight in an urban area.

For our first long drive, we reset the trip computer while on the freeway, and give the car a chance to achieve its maximum fuel economy. Because of the time involved, we drive a greater percentage of our miles on freeways and highways than on city streets, but strive for a realistic balance. However, we've found that the EPA estimates for cars tend to be accurate, so we merely use our observed fuel economy as a check on the EPA testing. Sometimes we find a large variance, but usually our mileage falls into the EPA range.

Freeway and highway driving lets us test most driver assistance features, such as adaptive cruise control, lane-keeping assistance, and blind-spot monitors. We consider how well these features do their jobs, how easy they are to activate, and what it takes to override them. In urban environments, we can test features such as automated parking, backup cameras, and, to some extent, collision prevention systems.

In the city, we test a car's maneuverability and throttle response, in relation to how quickly we can take advantage of an opening in traffic, or get around a double-parked truck in our lane.

The real fun comes when we get the car on a winding mountain road, quite a number of which are available in the San Francisco Bay Area. Not all cars are designed for this type of driving, but we take the majority out on such roads to feel the handling. The curves let us feel for suspension wallow or firmness, steering response, and shift times for manually selectable automatic transmissions. Putting a car through these paces, we can understand the engine's limits, and feel the effect of different sport settings.

Reaching conclusions
Our automotive testing tends toward the subjective. However, our editors drive about 100 new cars per year, so we use this accumulated experience to compare handling and responsiveness, as well as cabin electronics.

We reward cars for high-tech features both in the cabin and in the drivetrain. Our ideal car is one that uses advanced technology to get superior fuel economy while putting down a satisfying amount of power. Its steering should be responsive and it should offer a comfortable ride, but we also like cars that handle well in hard cornering.

While covering the basics for cabin tech, such as navigation, phone, and digital audio, a modern car should also go above and beyond, with useful connected and driver assistance features. The cabin interface should be as responsive and functional as a smartphone. Finally, we will certainly be swayed by an attractive design.