Often, parents and friends will park on the side of the street with their vehicles running as they oversee Trick-or-Treaters. Kids crossing the road in front of the vehicles are often blinded by the glare of the headlights and choose to glance quickly or look away and cross the road. Combine this with the limited visibility of some costumes, and you have a potential for a pedestrian/vehicle accident.
If possible, use only park lights when parked, and consider using hazard lights in busy places. Shutting down the vehicle will not only save gas, but also cut down on those nasty exhaust fumes.
While waiting, always keep your interior car light on. Many drivers suspect an open car door and will slow down just in case.
Pass on this safety tip to your community so that everyone will have a fun and safe Halloween.