A Brisbane bus driver has facial injuries after being headbutted by a passenger who was asked to show his concession card.

Police said the city-bound bus stopped at the intersection of Cavendish and Creek roads at Mount Gravatt East on Brisbane's southside about 6:00pm on Saturday to collect two young passengers.

As the teenage boy and his female companion boarded, an argument erupted between the 67-year-old driver and the boy, who then headbutted the driver.

The boy and a female companion got off the bus and were last seen running down Cavendish Road.

The driver was taken to QEII Hospital with a facial wound and possible fracture.

Rail Tram and Bus Union spokesman Tom Brown said it was an unprovoked attack.

"He wanted a concession and the driver asked him to see a concession card," he said.

Mr Brown said there were fears the driver had a fractured eye socket, but X-rays had cleared him of serious injury.

"He's now on 48-hour complete rest and then back to the doctor," Mr Brown said.

He said it was too early to say if the driver would return to work behind the wheel of council buses.

"My experience has been it's a difficult step back once something like this happens — once it kicks in mentally how close it came to something more serious," Mr Brown said.

Greater security needed

Police are investigating the incident, which comes days after the release of a report on bus driver safety highlighting the vulnerabilities of the job.

The Deloitte report recommended barriers around bus drivers to protect them from violent passengers, and more senior network officers.

Mr Brown said the attack highlighted the need for greater security, including protective screens and more security officers for drivers' safety.

"We really need this because this is a daily thing for our drivers … and sooner or later it's not going to end as well as this time," he said.

"We really need to have a trial so that we've got an effective barrier and something that's acceptable to the driver.

"Certainly we don't want cages or something slapped in there because it wouldn't solve the problem."

The union and the Brisbane City Council are still trying to resolve a dispute over pay and conditions, with industrial action being taken over the last few weeks, including some drivers going on strike or refusing to collect fares.