BT is expanding its network of public Wi-Fi sites across the UK with access points in 500 McDonald's restaurants.

By the time rollout is complete at the end of March, BT will have 2,200 Openzone access sites across the country.

The McDonald's sites will mainly be at the company's drive-thru restaurants, in addition to its flagship locations in London. Drive-thru restaurant customers tend to park nearby to eat their food, and will be able to access the Openzone service on their laptop or PDA if they are within 100 metres of the site, according to BT spokesman John Carter.

The Openzone service costs from £10 a month for 120 minutes of access on a subscription basis, or 20p per minute on a pay-as-you-go system, at any Openzone site. These include Costa coffee shops (owned by Whitbread Plc), Hilton hotels, Welcome Break motorway service stations and BAA airports. Users can also buy £6 vouchers at each site, giving one hour's access.

Hotels have the highest Openzone use, Carter said, although he did not have details of how long users spend online in different locations.

BT isn't the only wireless access provider looking to expand its public sites in the UK. Starbucks coffee shops began a rollout of Wi-Fi access, through T-Mobile, last February after performing successful trials in six locations.

The service is very popular, according to one employee at a small London outlet. "We just got it two weeks ago, and it was a relief because we had been having to send customers to a bigger outlet at Leicester Square," according to the Starbucks employee, who asked not to be named. The most popular times for people using the service are the early mornings and evenings, he said.

McDonald's was not immediately available to comment on how long the average customer spends in a restaurant or parked in the vicinity.

The McDonald's rollout will be too late for BT's planned promotional Wireless Broadband Week, however, which starts on 26 January. During those seven days, BT will offer free access, with no time limit, through its access points.