INDIANAPOLIS — Six Indiana State Police trooper vehicles in the Indianapolis district have been hit in just the last five days, all while responding to other crashes on icy roads. WATCH FULL STORY BELOWISP sergeant calls it 'heartbreaking' as 'selfish' drivers hit trooper vehiclesThe incidents come as troopers have investigated more than 600 crashes in the last five days in the Indianapolis district, according to ISP Sergeant John Perrine. The ISP vehicles were hit while the troopers were on the side of the interstate responding to another crash. On Thursday, plow truck drivers are emptying salt from their trucks at their Indianapolis substation because the extreme cold temperatures make salt ineffective. Anytime it's under 15 degrees, our salt really isn't effective.