Officers closed the road for 15 minutes and joined the search for Millie who was last seen running up the A27 towards Farlington Marshes, on the evening of January 15.
A spokeswoman for Hampshire police said: ‘They received numerous calls from motorists who had stopped on the A27 to try and catch the dog. With so many people abandoning their cars in different locations, which was then causing safety issues for other road users, officers attended.
‘The road was closed for around 15 minutes to get the traffic slowed down and people back to their cars.
‘Unfortunately the dog hasn’t yet been located.’
In a tweet on Saturday the Hampshire Roads Policing Unit said: ‘’We've been out on the A27 near Havant looking for Millie a Jack Russell. Last seen running up the A27 towards Farlington Marshes. We have released the traffic, but if you see Millie please ring in on 101 #23701.’
