Is there safety in numbers?

According to Malcolm Gladwell the opposite is the case for police officers out on standard patrols:

An officer with a partner is no safer than an officer on his own. Just as important, two-officer teams are more likely to have complaints filed against them. With two officers, encounters with citizens are far more likely to end in an arrest or an injury to whomever they are arresting or a charge of assaulting a police officer. Why? Because when police officers are by themselves, they slow things down, and when they are with someone else, they speed things up. "All cops want two-man cars," says de Becker. "You have a buddy, someone to talk to. But one-man cars get into less trouble because you reduce bravado. A cup by himself makes an approach that is entirely different. He is not as prone to ambush. He doesn't charge in. He says, 'I'm going to wait for the other cops to arrive.' He acts more kindly. He allows more time."

- Blink, p. 234

Once you've encountered a situation in which you need to call for backup, it would seem that you're no longer on a standard patrol.