Green’s Dictionary of Slang

(US) a small police vehicle, a car or van; also attrib.

1949		N. Algren Man with the Golden Arm 86: The squadrol slid up beside him.
1968		D. Walker Rights in Conflict 234: A heavy woman in a muu-muu insisted on using the step at the back of the squadrol as a platform from which to address the crowd.
1971		R.T. Sale Blackstone Rangers 43: Them cops, man [...] hear this slangin coming out of our mouths and man, there they is, sitting scared inside some squadrille, clutching a shotgun’.
1972		E. Grogan Ringolevio 271: They brought Emmett around and dragged him into a squadrol.
1979		‘Iceberg Slim’ Airtight Willie and Me 195: He was stopped by uniformed squadrol officers.
2006		J.A. Jack Three boys Missing 215: The squadrol from Gale Street was in one of the parking bays, motor running and with the driver’s door open.