The northern Spanish town of Pamplona has taken novel measures to try to ensure the safety of participants in its annual bull-running festival.
A dozen people have been killed since records began in 1924
The town's cobbled streets have been painted with a non-slip coating ahead of the first run on Thursday morning.
Organisers hope this will lessen the chance of bulls slipping and crushing runners against the crash barriers.
The famous San Fermin festival lasts a week, with morning bull runs, afternoon bullfights and all-night parties.
At least 13 people have been killed in the bull run since record-keeping began in 1924.
Others are occasionally gored or trampled as up to six bulls and as many steers race along the 825m course towards the town's bullring.
Pamplona's authorities believe that preventing the animals from slipping on the cobbles will make them less angry, and so less inclined to attack the runners.
Up to 1.5m people are expected to attend this year's festival
The acid-based coating will also help the participants, many dressed in red and white, keep their footing and out-pace the bulls. The animals later face matadors in the arena.
The town has also issued 100,000 leaflets recommending the best way of approaching the bull run and warning of the dangers.
Some 1.5 million people are expected to attend this year's event, which kicked off on Wednesday with the traditional firing of a firework from the town hall balcony.
The BBC's Katya Adler in Pamplona says overcrowding, not to mention excessive alcohol consumption, add to the risks for those involved, many of whom come from around the world.
The festival - which has been held since 1591 - was brought to international attention by Ernest Hemingway's 1926 novel The Sun Also Rises.
Earlier this week, hundreds of animal rights campaigners - some dressed only their underwear - held a protest against the killing of animals in the bullfights.