Re-read the previous comments and noted that this method has already been suggested by dungbeetle. I can only add that also an instant flash/strobe device could be used to cause temporary eyesight impairment (like those grenades used by special ops). Either way seems that ambulances are long overdue to be treated in manner similar to police cars, possibly carrying even more of expensive equipment to guard, so any measure however aggressive it may seem should be good. I remember back in 2000 or 2001 in Edinburgh cases of ambulance crews being attacked by youngsters with... bows (arrows)... even injuring a crew... dangerours and dark world we live in. Keep up the good work!