A new police unit head ed by a newly appointed sergeant has been estab lished in Bensalem Town ship. Action by the board of supervisors this week estab lished the accident investi gation squad and promoted 10-year police veteran Alex ander Mackwatch to the rank of sergeant to head the unit. Police chief William F. Kiempp said the squad will consist of Officers William Johnson, John Robinson, Richard Chappell and Jef frey Jones with one as signed to each of the three daily shifts. They will be charged with an accident investigation and reporting assisted as needed by the rest of the township’s force. Chief Riempp said the squad, which he proposed to the supervisors, fits in well with the uniform acci dent report recently ap proved by the state’s police chiefs at their convention. He said the men will at tend workshops to be con ducted by the bureau of traffic safety next month. The forms go into use on Oct. 1, he said, “Instead of having 24 men responsible for traffic accident reporting,”’ Chief Riempp pointed out, ‘‘we will now have five and this should make control of the reporting a much easier task. Mackwatch, married and the father of a 17-year-old boy, will receive a $300 boost in salary for his new rank, to $6,260.