The organisers of the 2014 Tour de France Grand Depart have predicted that it will further boost the soaring popularity of cycling in Britain and put Yorkshire on the global map, as they begin their final six months of preparations.

With the event's profile higher than ever thanks to two consecutive British winners of the yellow jersey, organisers have said they expect the Grand Depart – returning to England for the first time since 2007 – to attract between 4 million and 5 million spectators over three days.

Sir Rodney Walker, who chairs the committee created to oversee the organisation of the event, is to publish the first of three reports on progress this week – before the "six-months-to-go" milestone on 5 January.

He said discussions were under way with Sport England and British Cycling about how best to capitalise on the further boost in profile that the world's most famous cycle race would afford the sport, after a period of exponential growth inspired by the heroics of Sir Chris Hoy, Sir Bradley Wiggins, Victoria Pendleton and others.

The route loops from Leeds to Harrogate through the Yorkshire Dales on its first day before travelling from York to Sheffield via Huddersfield on its second.

The report estimates that based on the experience of previous Tours, it would be reasonable to place the overall economic impact at more than £100m.

The third day will see the peloton move to Cambridge for the start of the third stage and finish in London. Between UK Sport, local authorities and Transport For London, about £27m has been committed to hosting the three stages, including £10m from central government.

But Walker said the benefit – in terms of the boost to local businesses, the impact on tourism and inward investment and a likely increase in participation – would be well worth the money.

"The reason Welcome to Yorkshire decided to bid was because they saw the potential for showcasing Yorkshire on the world stage. Estimates vary, but we're talking in excess of 1bn people in terms of the television audience and it will showcase Yorkshire in all its aspects," said Walker, a former chairman of Sport England, UK Sport and the Rugby Football League.

"It's also a wonderful opportunity for businesses, in the north and in Cambridge, Essex and London. Right now, the profile of cycling is at an all-time high. Part of what we're involved in is discussing with Sport England and other agencies about how we can leave a lasting legacy."

Recently released figures showed that cycling has overtaken football as the third most popular participation sport in Britain, with more than 2 million adults now riding regularly.

British Cycling is seen as almost unique among sports governing bodies in marrying elite success, including a rush of Olympic gold medals in 2008 and 2012, with increased participation.

Walker said there had already been huge public enthusiasm for the event and predicted it would grow as the date got closer.

Recent tours have brought increased fears over the security of the riders, with tacks left on roads and Manx rider Mark Cavendish squirted with urine.

Walker said the organisers had begun liaising with police and crime commissioners to try to head off any attempts to disrupt the race.

"They have no concerns at this stage but as we get closer they will be intelligence gathering. All the people I talk to are excited at the prospect of the event coming to Yorkshire. But you can't legislate for those who hold a different agenda," said Walker.

He said there was huge enthusiasm for the event and TdFHUB2014, the vehicle created to organise it, would shortly begin the task of recruiting up to 10,000 volunteers to marshal the route. He said the spirit of the volunteers at the London 2012 Olympics showed the level of enthusiasm among Britons for getting involved in big sporting events.

Many cycling clubs and charity organisations had already arranged to ride portions of the course, said Walker. "The first six months of next year will be all about the Tour de France," he predicted.

The Yorkshire bid, backed by the local tourism authority, beat rival pitches from Edinburgh and Florence to host the opening stages of the Tour.