Officers spotted the car travelling eastbound between Preston Island, on the outskirts of Shrewsbury, and junction seven of the M54 on Wednesday afternoon.
The occupants were suspected of being involved in a scam targeting elderly and vulnerable people across the county.
Two men and two women, all in their 20s, were arrested. They were later released on police bail.
A Detective Inspector involved in the investigation said: “All four were arrested as part of our ongoing operation and investigation into recent courier fraud attempts on elderly and vulnerable people across Shropshire.
“In these cases, individuals have been pretending to be police officers in attempts to get people, usually elderly and more vulnerable members of our communities to visit their banks and withdraw large sums of money.
"In some cases the demands have been made they take out up to £10,000.
"The criminal gang then sends a ‘courier’ to the victim’s house to collect the money. It is all part of an elaborate lie about their bank under investigation and they can be very convincing.
“These are cowards and spiteful criminals, preying on those often too scared to say no to someone they think is a police officer and abusing their trust in a service that exists to protect them from harm.
“The arrests are part of a much broader police operation and I want to reassure the public that we will not rest until this organised gang of criminals have been brought to justice.
“I would urge people to make sure their elderly relatives, neighbours, customers and friends are aware of this scam and to remind them please that no police officer will ever call them and ask for their money, no matter how convincing the person on the telephone may appear.
"If they do receive this type of scam call, hang up, wait 10 minutes and then call us on 101 and report it.
“If you think you have been a victim of this fraud then please, don’t be embarrassed, call us and tell us and we will investigate.”