Slow traffic is congesting a main route out of Northampton on the first day of works that will last until April.
Horse Market, near the St Peter's Way roundabout, has one lane closed while National Grid carry out gas main replacement work.
Live traffic maps show the area has been experiencing particularly slow traffic in Horse Market - as well as queues on the road between the roundabout and the train station - since about 4pm.
Workmen are carrying out gas maintenance in the road to replace old iron gas mains with more durable plastic pipes "to ensure we continue to provide safe and reliable gas supplies to local businesses and residents".
The scheduled finish date is April 3.gas works traffic map