A portable traffic control unit comprising a wheeled trailer having a main frame attachable to a towing vehicle. A telescoping, vertical mast carries a pivotally mounted boom assembly. A first traffic control signal is secured to the vertical mast and a second at the end of the horizontal boom. A winch...http://www.google.de/patents/US4616225?utm_source=gb-gplus-sharePatent US4616225 - Portable traffic control signal device
