With no gears, less to go wrong. And with a fixed rear wheel, you can brake by not pedalling, so no need for bike brakes to make the handlebars look cluttered. A very minimal alternative to the mountain bike with hydraulic disk brakes, 6 inch front and rear travel -accessories that can only get stolen. Without even quick release wheels, there is little to get stolen. Hence, no need to lock up the wheels, or even the premium brooks saddle.
Before everyone rushes out to buy one, know that its illegal to use a bike on roads without two independent braking systems -a front brake is actually needed. Also, the requirement to push down the hill too, means that these are the worse possible bicycle for knees. Those mountain bikes are not just mid-life crisis bikes, they have the low gears you need as you age. Bear that in mind.
Single speed bikes do work in the city, though perhaps as they become more popular, the council should give away a new bristol bike map -one that does not show Nine Tree Hill on it
Without such information, single speed cyclists such as this one, may suddenly discover there is a 1 in 4 hill on their journey, and so be forced to get off and walk.