At any given hour, on any given day, legions of foot soldiers are negotiating traffic on Boston's gnarly maze of streets. They bring you lunch, dinner, and drinks, all with neatly packaged bundles of condiments and plastic utensils. Their day's work is a narrative of human eccentricities. They have the logic and foresight of champion chess players, the instincts of Navy Seals, the navigational skills of ambulance drivers. They don't have unions or pensions. They typically pay for their own gas. They live off tips.

They are the delivery drivers, workaday saviors, overcoming a host of urban perils: icy roads, oppressive heat, parking hassles, traffic, the gang of pre-teens across the street who seem to have no qualms over suddenly launching their skateboards onto the sidewalk. Indeed, one city slicker's convenience is another's challenge.

It's dangerous work. Every so often, one of them is robbed — or even stabbed (a 58-year-old Domino's Pizza driver was murdered in August 2010 when he made a delivery to a Hyde Park home). But they don't have to go it alone. They're helped out by a sizable support network, composed of others who dictate the rules of the street: the parking-lot attendants who wave them through, the building security guards who fend off the cops who are ready to pounce on a stalled car, the meter maid who's a friend of a cousin.

For the most part, the livelihood of these road warriors is based on constantly entering the unknown. Here are some reports from the trenches.

THE FAMILY MAN

Kan Wiwatyukhan, 22, still smiles disbelievingly when he tells about how, weeks before, a driver of a black BMW pulled over and told him, "Get in." Wiwatyukhan had been running down a Fort Point street, chasing a tow truck. The helpful stranger delivered him to the tow truck, which was stopped at a light. Wiwatyukhan forked over $100 cash to the truck operator and got his car back, food order still safely inside. "Towing — it sucks so bad when there's still food to be delivered in the car," he said.

That's just one of the hassles Wiwatyukhan faces daily, as he jumps in and out of his Acura TSX, dropping off pad Thai, crispy duck, and other aromatic dishes — some of which his mother prepares — to office and hospital workers, residents, hotel guests, garage attendants, and Amtrak conductors around the Financial District, South Boston, and elsewhere within a three-mile radius of Siam Bistro, his family's restaurant on the Greenway. Parking is another problem. In one year, he racked up $1500 in tickets and violations.

I went for a delivery run with him on a Thursday night. It was tax season — "wicked busy." He turned a corner and the car trembled as we drove over a ripped-up Fort Point road. "You see what we go through?" We pulled into a lot with two BMWs parked in front.

When he arrives at a customer's location, he calls and announces himself as "the delivery guy." Some people don't even tip him.

"What's not to understand? Delivery guys live on tips. We use our own gas, our own cars. We bring food to your door. If you don't want to tip, don't order delivery. Pick it up. Just $2 will keep a delivery guy from hating you."

Wiwatyukhan's family immigrated when he was 10. He got his start working at a cousin's restaurant chain in Weymouth, Ipswich, and Quincy for three years. Then his parents decided to open a restaurant, too, and Wiwatyukhan was deputized to do all the licensing and legal work on behalf of his family."They put money in front of me and said, 'Go open it,'" he said. The restaurant, which is two years old, now employs all three of his brothers, the youngest of whom, at 16, helps pack up orders after school. Wiwatyukhan has an associate degree in accounting from Bunker Hill Community College, and dreams of someday opening a garage for sports cars, but his plans for an advanced degree are on hold.

"I have to be here full time. To do that and school is tough. I had to drop out. The restaurant is the priority," he said. "Our income is from the restaurant. If the restaurant fails, the whole family fails."