How we measure

Acceleration · The Shove

A time-stepped launch: the engine or motor torque curve through each gear and the final drive, less driveline losses, limited by what the driven tires can grip as weight shifts rearward. Hybrids and turbos carry their own launch limits and lag. Power is calibrated so the simulated runs match instrumented 0–60 mph and passing times where a test exists; 0–60 times subtract the 1-ft rollout US testers use, so they compare with published figures.

Limits: one driver, no wind, a warm car on a good surface. Launch control, tire temperature and altitude are not modeled.

Braking and stopping distance · The Stop

Stopping distance is reaction distance plus braking distance. During the reaction time the car keeps its speed; the brakes then build to full force over 0.15 s and hold it to a stop. Full dry-road deceleration is calibrated to the car’s tested 70–0 or 60–0 mph stop. Wet and snow scale it by the friction the tires find on that surface. Pages use a 1-second reaction unless they say otherwise; the lab lets you change it.

Limits: straight line, fresh brakes, one deceleration for the whole stop. ABS cycling, brake fade, slopes and load are simplified or left out.

Rollover · The Tipping Point

The static stability factor is half the track width divided by the center-of-gravity height, the same quantity behind NHTSA’s rollover rating. From it we work out the sideways speed at which a car sliding into a curb would trip over. NHTSA’s star rating and rollover risk are shown as published; the curb speed is our illustration of the same geometry.

Limits: the center-of-gravity height is rarely published and is often estimated; suspension and electronic stability control are not modeled.

Efficiency and running costs · The Invisible Wall

At a steady speed the car pushes air (drag coefficient × frontal area × speed squared) and rolls its tires; dividing by the powertrain’s cruising efficiency gives energy per mile. Efficiency is calibrated to EPA ratings or instrumented highway tests. Yearly running cost uses the EPA rating, 15,000 miles a year and national average energy prices (EIA), the same inputs as the lab’s cost panel.

Limits: no wind, hills, temperature or climate-control load. Real-world economy varies more than any single figure.

Grip, snow and maneuvering · The Grip Budget

Each tire’s friction depends on the surface, the tire type and how hard it is loaded, with less grip for cornering than for braking (the friction ellipse). Cornering grip is calibrated to tested skidpad results where they exist. The snow figure is the acceleration the driven wheels can deliver on packed snow, which is why all-wheel drive matters there.

Limits: one tire per car as fitted to the trim; winter tires, tire wear and temperature are not modeled.

Space, luggage and fit · Live In It

Seats sit at positions fitted to the maker’s published head room and leg room; the roofline and floor come from the car’s 3D model or its published dimensions. We seat people of a given height using standard body proportions and measure the gap to the headliner and to the front seatback. The luggage test packs real suitcase sizes (75 × 50 × 30 cm checked, 55 × 40 × 23 cm carry-on) into the measured cargo box: large bags first, then carry-ons in the space left.

Limits: cargo spaces are modeled as boxes, so wheel-well shapes and odd corners are simplified; real bags squash a little.

Cabin noise · The Quiet Test

Cabin sound levels are Car and Driver’s instrumented readings at a steady 70 mph, in A-weighted decibels. When a trim wasn’t measured we use a tested sister trim and label it an estimate. About 1 dB is the smallest change most people notice, and repeat runs spread by about 2 dB.

Limits: one test car on one road surface; tires and options change the result.

Visibility · Can You See Me?

From the driver’s eye point (seat position and body proportions as in the space lab), we cast sight lines over the hood and through the windows of the car’s 3D model, or its fitted shape where no model exists. The result is how much road in front of the bumper the driver can’t see, and how much of the ground within 33 ft ahead is visible, for a 5 ft 9 in driver and a 4 ft 11 in driver.

Limits: mirrors, cameras and the driver leaning are not counted; seat height is set to the fitted position, not raised.

Headlights and night stopping · After Dark

IIHS measures how far each headlight system lights the road (to 5 lux) on a straightaway and on curves. We take the low-beam distance on the straightaway and find the fastest speed from which the car can still stop inside it, with a 1.5-second reaction to a surprise and the braking model above.

Limits: IIHS tests one headlight system per trim group; aim, dirt and bulb age change real reach.

Crash safety · The Impact

Crash ratings are NHTSA’s, IIHS’s and Euro NCAP’s, exactly as published, with the model years and test vehicle they cover. We never compute injury outcomes or scores of our own. The lab’s crash animations show momentum and energy only.

Corrections

Spotted something wrong or out of date? Email [email protected] with the car, the figure and a source.