Police have arrested a man who allegedly set fire to an Adelaide traffic camera overnight and then returned to try to burn it down again just over three hours later.

The speed camera at the intersection of Anzac Highway and Greenhill Road at Wayville was smashed and set alight about 12:20am.

The fire was quickly extinguished, but police said the suspect had driven away before patrols arrived.

Emergency services were then called back to the scene about 3:45am, when an attempt was made to set the camera on fire again.

"A suspect was arrested at the scene," Senior Constable Rebecca Stokes told ABC Radio Adelaide.

"It was the second time, we'll be alleging, that he tried to set fire to the same camera."

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The 40-year-old man from Reynella in Adelaide's south has been charged with two counts of arson.

ABC Radio Adelaide roving reporter Paul Culliver attended the scene, where he spoke to a police officer investigating the case.

"It's been attacked on two fronts — an attempt at burning it and also smashing the glass," he said.

"We have what we understand are burnt-up jocks, yes jocks, underwear, at the bottom and the fire has licked up the pillar on all four sides.

"Crime scene investigators are on their way because they obviously want to have a look at the forensics."

Video of the fire was filmed by two passers-by and has been posted on social media.

Senior Constable Stokes could not confirm reports the man used underpants.

"This is the first I'm hearing of it," she said.

The suspect's vehicle has been seized for forensic testing, and the man is expected to face court today.

There have been several attacks on Adelaide speed cameras in recent years.

In 2014, a man admitted to vandalising several cameras.

At the time, police alleged he had a crossbow that he was considering firing at them.

In August, a speed camera was reportedly torched on Tapleys Hill Road at West Beach.

Earlier this year, the SA Government launched an audit of fixed speed cameras after previously questioning whether locations had been chosen to maximise revenues.

The ongoing use of handheld speed guns was thrown into doubt after three drivers successfully challenged speeding fines.