Roughly half of the city’s 40,000-odd cabbies are Muslims who hail from countries all over the Middle East, Africa and elsewhere — and a great number of the drivers are observant, praying five times a day. Which raises the question: How and where do these men on the move pray? When you spend your days driving a taxicab, it’s impossible to say where, at any given moment, you might wind up. Followers of Islam can perform their five daily prayers in any relatively clean space, even bowed down on the side of the road. But the process isn’t so simple.