It has measured the outdoor sites at malls, supermarkets, pedestrian shopping areas, and motorway services across the country, using a GPS-based travel survey that now includes a sample of 34,000 people.

Participants are asked to carry a GPS device for a nine-day period, which tracks their locations every second. This GPS data is then matched to traffic patterns and street networks to build a picture of how people move around.

Once movements were mapped, Route and its research partner Ipsos MediaCT calculated the number of people that would pass any of the 450,000 outdoor advertising ‘frames’ that cover the UK, while eye-tracking research was used to work out the likelihood that a passer-by would notice the frame.

When Route launched last year, it only contained audience estimates for frames that lined the UK’s road, bus and tube network. It has since been expanded, and this new release of retail data covers 6,000 sites, at supermarkets and motorway services – including the largest 1,323 supermarkets across all parts of the country.

Route’s data shows that the average time spent in the vicinity of a supermarket is 31 minutes. It reveals that shoppers in the south west travel the furthest to visit a supermarket, with 8% making a journey over 25km. Three percent of the whole population travel 50km or more to a supermarket, but most of us travel no more than 5km.

According to Route, the average weekly audience for a frame in a supermarket parking area or entrance is 20,610 people, with 60% of this audience viewing the ad while in a vehicle.