The incident occurred on Wednesday evening on the Edinburgh City Bypass where a lane is blocked eastbound at Dreghorn.
Traffic has been disrupted following the crash, with reports delays of around 60 minutes.
Traffic Scotland alerted motorists on social media at 5:06pm, posting on Twitter: “Lane 2 (of 2) is blocked E/B at Dreghorn due to an RTC.
“Lane 1 is partially blocked, traffic is getting past on the hard shoulder.
“Police & TRISS en route
“Traffic is slow from Baberton”.
A Police Scotland spokesperson said: “Around 5.10pm on Wednesday, 2 June, officers were called to a report of a four car crash on the A720, Edinburgh by-pass near the Dreghorn junction. Ambulance also attended.”
Meanwhile, Traffic Scotland has reported another crash on the M8 westbound.
Posting on Twitter, Traffic Scotland wrote: “Lane 2 (of 2) closed W/B at J3a due to an RTC.
“Emergency services on scene.
“Traffic is slow tailing back to J3 - approx 20 min”.
More to follow.