Highways England wants turn the hard shoulder into an extra lane between junction three by Heathrow Airport and junction 12 at Theale to tackle periods of heavy congestion.
The scheme, costing up to Â£862m, will improve traffic flow and ensure "less stressful driving", supporters say.
Opponents claim it will increase congestion and affect the environment.
The motorways are called "smart" because technology will be installed to monitor traffic, provide information to drivers, and ease congestion by using variable speed limits and utilising the hard shoulder.
"Emergency Refuge Areas" will be put in place every 2.5 km (1.6 miles) so drivers can come off the hard shoulder and await recovery.
The first one was introduced on the M42 near Birmingham in 2006 and there is now also one on the stretch of M4/M5 near Bristol.
Chief scientist Alan Stevens at the Transport Research Laboratory in Crowthorne, which carries out modelling for the smart motorways, said: "They help the traffic go better, drivers get shorter and more predictable journeys and less stressful driving.
"We did a lot of modelling work and put people into driving simulators to see how they would respond, and actually we found no problems at all."
John Booth from Reading Friends of the Earth said smart motorways are not the solution to congestion.
"The reason they're doing this is they want to cater for more traffic on the motorway and will encourage more traffic growth, and that will have a knock on effect on air quality, on climate change emissions, on noise and on congestion on the non-motorway network," he said.
Following written representations for six months and a three-month public reaction period, the decision will be down to Transport Secretary Patrick McLaughlin.

Cerys Yemm, 22, was killed by Matthew Williams, 34, in November 2014 at the Sirhowy Arms in Argoed, Caerphilly county.
Williams was Tasered by police and later died.
PC Kelda Griffiths, who was the second officer into the bedroom, said Williams "didn't seem human".
She told the Newport inquest: "It was like something you see on TV, not something you expect to see in real life."
The inquest was told PC Griffiths knew Williams had a history of drug abuse, mental health problems and of previous violence towards the police.
She said she had refused to enter the hostel without back-up.
"I just believed that maybe he had staged an incident because it was so unreal, as that he wanted to get so many police officers there and attack the police," she said.
"It was such an unbelievable, surreal call. He had murdered someone and I have no doubts that he didn't like police and we would have been next - definitely."
Lawyers for Ms Yemm's mother quizzed the officer over the wait to enter the Sirhowy Arms, telling her: "Mrs Yemm is tormented by the idea that your delayed attendance may have resulted in her daughter's death."
But answering questions from Gwent Police's legal team,  she confirmed she had been instructed to meet another Taser-armed officer before entering the hostel, which she said led to a wait of "no more than a minute".
The officer said Ms Yemm was dead when she entered Williams' room - where the killer had already been Tasered.
"As I stepped into the room I recall seeing Cerys's face, which was horrific," said PC Griffiths.
Despite being hit with the stun-gun, PC Griffiths said Williams continued to struggle.
"He was lashing round and banging his head on the floor. There was no stopping him. He had unbelievable strength," she said.
She told the inquest fellow officer Alan Cotterell used his Taser again after urging Williams to calm down.
"Even with four of us there he was lashing around," said PC Griffiths.
She said PC Cotterell fired his Taser into Williams' back or side.
The inquest on Thursday heard another officer say Williams was Tasered "four times".
PC Griffiths said after each time the weapon was used, Williams would stop struggling, but added: "After a few seconds he would start struggling and biting."
She said after the final Taser shot "he did start to go calm", was put in a recovery position and monitored.
"He was breathing," she added.
The inquest continues.
A planning inquiry is under way to create a "smart motorway" along the M4 in Berkshire.
[NEXT_CONCEPT]
A police officer thought she was going to die as she confronted a "demonic" ex-convict who had brutally murdered a young woman, an inquest has heard.