SAN DIEGO, Calif., Jan. (AP) ‘Office of Defense ‘Transportation officials here said today they were uncertain what effect the new ODT ban on use of vehicles to transport p assengers to horse races would be on the Agua Caliente, Mex., track. Willard Barr, San Diego DDT representative, said the new order announced In Washington had not arrived at his office, but assumed , pertained to automobiles owned by individuals in addition to busses and trucks. Barr agreed that, on the basis of information now available to him, the order might not have much ef fect on the Caliente track, be cause Most motorists already park their cars on this side of the inter national line and use a Tijuana taxi to reach the track, three miles from the border. at Barr said racing fans using a common carrier in Mexico to the track apparently would not be vio lating the American ruling, but that persons driving their cars to the track could be reached. a Customs officials have estimated , what only a small percentage of, the persons crossing the border at. 3ar Valdro into Tijuana attend the races. Most of the travelers arel« oariats on shopping or sight-seeing t ips, '