London Olympic organisers could charge spectators to watch part of the road cycling, an event previously assumed to be free, because of environmental issues, they said on Friday.

Hundreds of thousands of spectators are expected to line the 250-km men's route on the opening weekend of the Games, lured by the prospect of Britain's first gold medal in Mark Cavendish, and a free view.

But the organisers, LOCOG, are considering asking around 15,000 fans to pay for the privilege of watching the men's and women's races from one of the best vantage points along the route through the Surrey countryside, the Zig Zag climb of Box Hill.

The races on July 28 and 29 include a circuit of Box Hill which the men will ride nine times and the women twice.

It will be ticketed, Debbie Jevans, London 2012 director of sport told Reuters on Friday.

We are looking at the tickets and how we manage that and it will be announced shortly, once we have got through all of our test events and looked at numbers then we will announce the process for those tickets.

We are assessing it and will manage it in the most appropriate and best way, she added.

The prospect comes after LOCOG was asked to consider cutting back on the number of tickets for the equestrian cross-country event at Greenwich, south London, because of concerns over transport congestion.

It had been expected cycling fans would only be charged to sit in the grandstands at the race start and finish outside the Queen's central London residence of Buckingham Palace.

DAMAGE CONCERNS

The road race had already courted controversy after organisers initially said only 3,500 spectators would be allowed on the Zig Zag road because of concerns over damage to the protected National Trust grounds.

Revised plans to increase the number of spectators around Box Hill were announced by LOCOG last month.

What we need to make sure is that we maximise the number of spectators we have while taking into account that it is an SSSI (Site of Special Scientific Interest), Jevans said.

So what we are doing is quite rightly paying attention to the area itself and how special it is and that we manage it appropriately.

Britons will be hoping the men's road race will throw up their first gold medallist with Tour de France multiple stage winner Cavendish expected to be in the saddle.

I don't think it is a scandal, Italian Manuel Quinziato, one of the BMC riders who helped Cadel Evans win last year's Tour de France, told Reuters by email.

Nobody is surprised when 70,000 pay to watch the cyclocross world championships. That's just a sign that the Olympics are always more about money.

Team GB cycling principal David Brailsford declined to comment.

Fans have already been left disappointed after failing to secure tickets for events in the Olympic Park. Cycling in the Velodrome was among the many events to be sold out within days of going on sale.

Organisers also came in for criticism for charging sailing fans to watch the regatta from a popular public area in Weymouth and Portland on the south coast.

(Reporting by Avril Ormsby; Additional reporting by Alan Baldwin and Julien Pretot; editing by Alison Wildey)