Surface texture of NASCAR tracks (smooth to rough)

From concrete tracks that are smooth as silk to ones that are as gravelly as Clint Eastwood's voice, NASCAR has a wide variety of racing surfaces. The sanctioning body regularly measures those surfaces and gives them a rating (in micrometers, for the variance between the highest peak to the lowest valley). The lower the variance, the smoother the track, and thus the lower the number. For more information on how the process works, read the story. For the full list (from smoothest to roughest), click through the slideshow. (Source: NASCAR R&D Center)

Martinsville Speedway, 118 micrometers (the smoothest track)

Dover International Speedway, 120

Bristol Motor Speedway, 128

Watkins Glen International, 168

Michigan International Speedway, 216

ISM Raceway (Phoenix), 227

Pocono Raceway, 232

Kentucky Speedway, 245

Chicagoland Speedway, 269

Indianapolis Motor Speedway, 276

Texas Motor Speedway, 285

Kansas Speedway, 334

New Hampshire Motor Speedway, 342

Talladega Superspeedway, 342

Las Vegas Motor Speedway, 345

Daytona International Speedway, 348

Darlington Raceway, 374

Charlotte Motor Speedway, 397

Sonoma Raceway, 436

Richmond Raceway, 456

Auto Club Speedway, 459

Homestead-Miami Speedway, 499

Atlanta Motor Speedway, 682 (the roughest track)