"If you can't correct it in any other way, you may have to grind it." It was not long ago that this advice about how to make a rough surface on new concrete smooth enough to meet tolerances was generally received as bad news. Now things have changed. Members of the International Grinding and Grooving Association (IG and GA) are routinely smoothing out new pavements. To correct roughness produced by faulting of the joints, members of Concrete Grinding and Grooving Inc. of Walnut Creek, California, used a bump cutting machine in 1970 to give new life to 8.3 miles of old two lane concrete pavement. Twenty feet long and weighing 30,000 pounds, the machine smoothed a 6 foot swath of pavement in one pass with 360 diamond-tipped blades. The rehabilitated pavement was incorporated into the new I-460 route between San Jose and Warm Springs. The bump cutter, powered with twin 276 horsepower diesels and running on crawler tracks, trimmed one-third to three-fourths of an inch off the surface of the concrete slab and completed the project within a time limit of 50 days. Interference with traffic was minimized by grinding at night and simultaneously using a vacuum system that cleaned the pavement by sucking up the slurry produced by grinding. Another major undertaking by members of the IG and GA is the improvement of skid resistance by grooving of highway and airfield pavements for greater safety. The same machines are used with different spacings of saw blades.