Due to the site of where the work has to take place, there will be disruption to the car park area immediately outside the main entrance of the hospital.
There are contractor compounds on site and some temporary arrangements in place for pedestrians and car users.
A Barnsley Hospital spokesperson said: “The contractor’s compounds occupy various areas.
“Since they have been established we have changed our drop off and pick up location at the front entrance of the hospital.
“A new pick-up/drop-off area has been temporarily established outside our outpatient entrance, just in front of the main entrance.
“We apologise for any inconvenience this may cause we hope you agree our extended and improved critical care unit will be worth this disruption.”