The A647 Stanningley Bypass is said to have a 'fold' as 'big as a speed bump' by witnesses as one lane is closed and the speed limit has been reduced.
The hump has appeared on the inbound carriageway near Bramley and Leeds City Council emergency team said on social media site Twitter that repair works will begin in daylight hours.
It is thought it appeared on Tuesday evening.
The outbound carriageway is said to be unaffected.
The tweets said: "#A647 Stanningley bypass. Reports received of a buckling of road surface nr #Bramley slip road. Potentially across East and West bound carriageways. Highways depot have been informed. Please take care and reduce your speed @WestYorksPolice @LeedsCC_News
"#A647 update. Leeds inbound carriageway nr #Bramley Henconnor Ln slip affected by buckling. Reduced speed limit and single lane closure in place. Works to repair will be carried out in daylight hours. Expect some delays to journey times. Outbound unaffected."