The "very confused" pensioner was stopped by police up on the 70mph-limit road near Crawley, West Sussex, on Friday.
Officers were alerted by a motorist who had seen the man heading away from the M23 on the A2011 Crawley Avenue and had stopped to help him.
PC Katie Breeds, of Sussex Police, said: "He didn't know where he was.
"We sat him in the back of our police car and waited for a colleague in a van to collect the mobility scooter and then we delivered scooter and driver back home to his warden-assisted accommodation in Crawley."

The 24-year-old was released by the Saddlers in May after 19 appearances in three years and has now joined their League One rivals.
"My main aim is to rectify what happened at Walsall," MacGillivray told the Shrews' official website.
"I didn't play as many times as I wanted to and that's what I want to do here, playing as many times as I can."
MacGillivray, who has also played for Stalybridge Celtic and Harrogate Town, is Paul Hurst's seventh signing of the summer.
Defender Zak Jules, midfielders Jon Nolan and Ebou Adams, winger Daniel James and forwards Arthur Gnahoua and Lenell John-Lewis have also been added to the squad.
Find all the latest football transfers on our dedicated page.

It is the first professional contract for the former Bristol Rovers trainee.
"When my agent told me that Forest Green were interested I was totally thrilled," Davies told the club website. "I can't wait to get started."
Forest Green - who finished second in the National League in 2015-16 - gave a first senior deal to 18-year-old striker Olly Mehew last Thursday.

BlackRock director Jonathan Paul Burrows was caught by inspectors at Cannon Street station last year and admitted to avoiding the £21.50 fare from Stonegate in East Sussex.
In total, Mr Burrows is believed to have dodged £42,550 in fares.
The City watchdog said he "demonstrated a lack of honesty and integrity".
"Mr Burrows has admitted that, on a number of occasions, he deliberately and knowingly failed to purchase a valid ticket to cover his entire journey," the Financial Conduct Authority (FCA) said.
"As Mr Burrows held a senior position within the financial services industry and was an approved person, he should have been a role model for others and his conduct has fallen short of the standard expected for someone in his position," the organisation added.
Mr Burrows avoided paying the full fare by boarding the London-bound train at Stonegate - a rural station with no barriers - without purchasing a ticket.
On arriving in London, he went through the barriers at Cannon Street Station using an Oyster travel card, incurring a maximum fare of £7.20.
Mr Burrows, who is now banned for life from working in any regulated financial industries, has since paid back the £42,550, plus £450 in legal costs.
Reacting to the FCA's decision, he said: "I have always recognised that what I did was foolish. I have apologised to all concerned and reiterate that apology publicly."
However he added that "the size of the settlement [with Southeastern] could be said to have led to a distorted perception of the scale of my wrongdoing".
"While I respect the FCA's decision today, I also regret it, coming as it did after a 20-year career in the City that was without blemish.
"I recognise that the FCA has on its plate more profound wrongdoing than mine in the financial services sector, and I am sorry that my case has taken up its time at this critical juncture for the future of the City and its reputation."

The 30-year-old played for the county in 2011 and helped them reach the final of the domestic T20 competition and the Champions League semi-finals.
"I enjoyed my time in Taunton and I am really looking forward to working with Matt Maynard again," he said.
"For me to be coming back to Somerset to contribute in all forms of the game is awesome."
Van der Nerwe previously played under Somerset director of cricket Matthew Maynard in the Caribbean Premier League, for St Lucia Zouks.
He has represented South Africa at international level, but now plays for the Netherlands and is currently involved in the ICC World T20 qualifier.
A 92-year-old man was found riding his mobility scooter on a busy dual carriageway after taking a wrong turn.
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Shrewsbury Town have signed former Walsall goalkeeper Craig MacGillivray on a one-year deal.
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Forest Green Rovers have signed Wales Under-19 international striker Blake Davies on a one-year deal.
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A London hedge fund manager who regularly avoided buying a train ticket on his commute to the City has been banned from working in the financial services industry.
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Somerset have signed all-rounder Roelof van der Merwe on a two-year contract to start next season.