Mr Campion said it was amazing there had not already been a major crash. "Obviously other drivers, in avoiding these people, have been travelling at a safe speed and had time to take avoidance measures."
Mr Campion said most complaints involved elderly drivers, although no one got a clear look at the driver in Tuesday night's incident and no registration number was recorded.
His advice: "If you realise you're on the wrong side of the road, pull over and stop," Mr Campion said.
Police have spoken to two of the 11 drivers.
"For one of the drivers, a medical review as to their fitness to drive is in process. With the other one they were warned, turned around and sent on their way."
NZ Transport Agency's Tauranga highways manager Niclas Johansson said it was concerned and looking into ways to prevent people making the mistake.
"Human error does occur from time to time, but the last thing we want is for a simple mistake to turn into a tragedy."
An independent safety specialist was now reviewing the entire highway to see if there were any possible changes that could be made to stop the confusion.
"The signage and road layout on and around the TEL meets transtasman safety guidelines, however as a few people have driven the wrong way on the road we're looking into ways to further prompt motorists and prevent any more confusion," Mr Johansson said. "At the Domain Rd interchange the two large, red signs on the off-ramp that say 'Wrong Way Go Back' ... have been lowered so that they are more in a driver's line of sight. "At the Mangatawa interchange additional road markings and signage have been added and the traffic lights modified, with green arrows added to make it even clearer to motorists which way they should turn to get on to the TEL."