West Sussex Fire and Rescue sent four fire engines and a command support unit to the scene.
A 75-year-old woman was airlifted to hospital following the crash in Arundel.
The 62-year-old, sister-in-law of actor Mackenzie Crook, went missing from her home near Arundel.
Laurel Aldridge, sister-in-law of actor Mackenzie Crook, vanished from her home on 14 February.
Laurel Aldridge, described as "very vulnerable", has gone missing from Arundel in West Sussex.
National Highways says it has modified the plans after comments from residents of three villages.
