A police booze bus caused traffic chaos in Nedlands yesterday morning after it was set up on Mounts Bay Road.
The random breath testing began about 7.30am near the Elizabeth Quay roadworks and caused traffic to stretch back to the Narrows Bridge despite the Labour Day public holiday.
Police said traffic started to build about 9.30am and the booze bus was shut down at 10.30am after officers conducted 516 random breath tests and 53 drug tests.
A police spokeswoman said statistics on the number of people charged with drink driving and drug offences would be available today.
Double demerit points were in place from Friday to yesterday.