The company which is set to frack for gas on a site off Preston New Road near Little Plumpton was held up for an hour by protesters.
The members of various groups opposed to hydraulic fracturing for natural gas in deep lying shale rock prevented workers from putting up safety fences at the start of the day.
They said the workers had, on previous days, placed them too far across the A583 which meant that there was not enough room for ambulances to pass the temporary road works against on-coming traffic.
Tina Rothery from the Lancashire Nanas group said: "Having witnessed three ambulances delayed in recent days, we felt we needed to take action. This is very serious. This is a main road used by ambulances on emergency calls when any delay could be a matter of life or death.
"The ambulance yesterday was held up by four oncoming cars and could not get through which is not acceptable. The fences were right up to the second white line in the road which meant there was not enough gap left. We think the measures here are not adequate."
Another one of the protesters at the site Gayzer Frackman said: "I stood in front of the fences to hold them up for an hour. They have been putting them right in the middle of the road which means it is difficult for emergency vehicles to get through at all times."
Shale gas exploration company Cuadrilla is preparing the site on a farmer's field for it drilling rig which will arrive later this year. They have agreed a procedure with the local protesters whereby they are aloud to walk in front of delivery wagons to slow their progress for 15 minutes as a protest in the safety lane where they turn onto the site.
A Cuadrilla spokesman said the protest was needless as the temporary traffic lights and fences were working as they were meant to and the work at the site was on schedule.
They said: "The claim that the fences are “too far across the road” are incorrect. Each day they are erected at the boundary of our roadworks, as agreed with Lancashire County Council Highways Authority, for the safety of all road users.
"This creates a single lane for traffic which is managed by temporary traffic lights and the emergency services are aware of this so they can factor it into their journeys.”