Our intrepid detective has managed to capture a reasonably high ranking operative from the "Big Bad Organisation". He was captured in an area of the city built in such a way a car can not be brought in to transport the prisoner. Think close buildings, apartments with balconies, lots of people in the public areas.
Previously "Big Bad Organisation" has killed operatives who have been captured. The detective needs to get the prisoner back to the police station with out getting him killed. The prisoner would prefer to live. He won't kill him self, he is loyal but not that loyal. If he can escape he will however.
Assume near future levels of technology, guns and knives are the usual tools of "Big Bad Organisation". They are not going to blow up buildings. If they make a hit they prefer not to take out any police or bystanders, just the target. Killing police brings bigger investigations which they would prefer to avoid. The police have had to do this sort of thing a few times before and have training and equipment to make it easer.
The solution I have come up with is a kind of armoured box on a segway thing to put the prisoner in. Every thing else seems to end up with a sniper shot from a window or a bullet from a crowd. Think of some thing like an old police box (The thing the TARDIS looks like) on two wheels and a bit smaller to fit through door ways.
Does this seem like a good solution to the problem? Stairs are an issue. If the prisoner was not cooperating would he be able to throw his weight around enough to topple the thing?
It seems a bit brutal putting the prisoner in effectively a metal coffin, is this a likely solution in an otherwise reasonably polite and free society?