Drag racers need to do pre-race burnouts to warm up their cars' tires, and line lock makes that easier by locking the front brakes while letting the rear wheels spin. This ensures that the car remains stationary during the burnout. While aftermarket systems require modifying a car's brake hydraulics, Ford does everything with software.
Ford envisions the system as a tool for weekend racers, who driver their Mustangs to work during the week and want to be able to go to the local drag strip and make some passes without having to modify the cars.
Line-lock joins a list of features--including launch control--that make the 2015 Mustang the most high tech ever. However, purists will be happy to know that the line-lock feature can be disabled, so drivers can still smoke their tires the old-fashioned way.
Electronic driver aids aren't the only controversial items on the 2015 Mustang's spec sheet. While it should have significant performance benefits, the independent-rear suspension may not get a warm welcome from drag racers, who tend to prefer the old live-axle setup. Maybe standard electronic line lock is Ford's way of reaffirming its commitment to the quarter mile.
Both hardcore racers and weekend warriors should read the fine print on their Mustang warranties, though. Even though line lock is a standard feature, and Ford says it should only be used on a track, actually racing your 2015 Mustang will void the warranty.
_______________________________________

• April 21: GM assembles its 100 millionth U.S.-built car on this date in 1967
  
  
  
  Few companies ever reach the dominance that General Motors held on this date in 1967 when it marked the 100 millionth car it had built in the United States at the Janesville, Wis., plant. That year, GM employed some 740,000 people, and was not just the largest automaker in the world but the largest company period. Its market share of the U.S. auto industry was more than 50 percent. Today, the blue Chevy Caprice coupe resides in GM's museum in Flint, Mich.; and while GM still ranks among the world's largest automakers, 1967 was a peak of sorts. Had GM's profits kept pace with inflation since then, it would have made $13 billion last year instead of $3 billion — although its hard to top the year Chevy introduced the Camaro
  
  Motoramic
• 1967 (1 of 10) CAMARO! a Jam Handy Film - YouTube