IT IS a humid afternoon, and two young police officers patrolling one of the roughest parts of Philadelphia have stumbled on something new. In a corner lot, a small brown horse is munching on thorn bushes. “I think it’s legal to keep a horse in the city,” says Mike Farrell, looking up and the down the block for clues. “You get used to seeing everything in this neighbourhood,” adds Brian Nolan, his partner, “but this is pretty unusual.” After learning from a passer-by that the horse’s owner lives nearby, and that its corral belongs to his grandmother, the officers extract a promise to ensure that the animal gets fresh water, and move on.

Philadelphia is a violent city, with a murder rate more than four times New York’s. To curb the mayhem, the police are resorting to an old-fashioned technique. Instead of insisting that officers cruise around in cars, the city is sending rookies out on foot. If they constantly patrol the same troubled neighbourhood, goes the theory, they will understand it better and keep it safer. The results are encouraging.

Mr Farrell and Mr Nolan patrol the 22nd district, one of the roughest. A four-square-mile warren of densely packed terrace houses and public-housing projects, it saw 35 murders last year, not to mention many robberies, assaults and crack deals. The pavement is littered with broken glass, crack baggies and ketchup packets. Hip-hop and soul blast out of open windows and parked cars. The streetscape is punctuated by barbers’ shops, storefront churches, kerbside cookouts, card games under gazebos, makeshift basketball backboards nailed to telephone poles and burned-out, abandoned houses.

But the officers, square-jawed white men in a nearly all-black neighbourhood, don’t balk at their surroundings. They kick balls with kids, banter with families sitting on front steps and rouse drunks from the steps of boarded-up shops: “Are you OK, ma’am? Are you diabetic? On drugs?” By talking to locals, they foster trust. “Jazz the Barber”, who owns a local salon, is appreciative. “They makes the area safer,” he says. “There used to be lots of robberies and home invasions around here. But now the police are seen, as opposed to when they’re just driving past. I think it’s cool.” Patrolling the district can be an eye-opener for new officers, says Sergeant Bisarat Worede, who has been in charge of the foot patrols since late 2010. It shows rookies that there are good people even in bad parts of town. And it seems to work. By mid-June there had been seven homicides in the 22nd district in 2013, compared with 20 at that point last year. Burglaries had dropped from 373 to 283, aggravated assaults from 352 to 304, and 54 people had been shot, against 77 in 2012. Philadelphia’s foot-patrol strategy was developed after a study in 2009 by criminologists from Temple University, which is in the 22nd district. A randomised trial overturned the conventional view that foot patrols make locals like the police more and fear crime less, but do not actually reduce crime. In targeted areas, violent crime decreased by 23%.

Crime has been falling in many cities, and for a variety of reasons. The population is ageing. Police are using data more shrewdly. Private security has proliferated: shops have cameras, houses have burglar alarms and cars have immobilisers. It is hard to disentangle the effect of any single crime-fighting technique. But foot patrols have some thoughtful backers.

Such patrols work best if officers return to the same street several times in each shift, says Jerry Ratcliffe, director of Temple’s Centre for Security and Crime Science. A good officer will soon know everybody on his beat. It is important to “spend time just standing on a street corner, chatting to people, getting a feel for the tempo and rhythm of a place.” Foot patrols work best in dense neighbourhoods, says Mr Ratcliffe, where many people cannot afford air conditioning and so socialise on the street. Drunken disagreements beget violence. “Half the people shot in Philadelphia are shot within two blocks of their address,” he says.

Officers in cars perceive a neighbourhood differently, he continues. They are typically only exposed to people who are under stress: suspects or victims of crime. “Whereas when you’re on foot, there’s a lot more opportunity to interact with normal people. People who just happen to be living in a poor or violent area.”

Not everybody in Philadelphia’s 22nd district welcomes the beat cops. “They walk around with attitude,” says Nasir Brown, sitting on the kerb with a friend as Officers Farrell and Nolan pass. “They’re attacking the wrong issues. Don’t nobody in the ghetto manufacture drugs.”

But others are happy to see the officers. Asked how their presence has changed his neighbourhood, Keenan Jones says: “Well, me and you can talk right here right now without no gunshots going off.”