At the heart of any gustatory ramble is a simple truth: When the streets are filled with people, the streets are filled with food.

	Lucy Sheets pours sauce on a hoagie at her stand in the 2100 block of Penn Avenue in the Strip District. (Krista Schinagl, Post-Gazette)

Just wash that bite of mustard-painted hot dog down with a cold swish of fresh-squeezed lemonade -- both from the corner cart that smells so heavenly every time you cross the street -- and you'll be glad you live in urban America, where enterprising individuals bring their culinary passion to the pavement.

Street food is edible regionalism, and the flavor of a city is found in its streets. In Chicago, the fragrance of roasted corn, rubbed with spices, fills the air. In San Diego, wrap your sandy hands around a beachy fish taco. Pittsburgh's own favorite street food, an Americanization of our Central European heritage, is the giant sausage sandwich.

With increased pedestrian traffic and pleasant weather comes a wash of colorful businesspeople: the hawkers, the vendors, the salespeople of street food.

Their places of business are square trucks with a side window -- ice cream trucks serving up dal and sesame chicken rather than King Kones. They dish from trailers unhitched, resting at a busy corner, or from a pushcart shaded by a colorful umbrella. Their uniform often includes an apron, gloves and a backward ballcap -- or whatever keeps them warm on a blustery day or cool in a portable kitchen when the mercury rises.

Easy to wheel away but fixed to the same spot every day, street food vendors lend a sense of continuity to a neighborhood. Plus, for less than $5, their quick eats are the cheapest thing going.

To find them, I took a multicultural tour of Pittsburgh's walking-est neighborhoods: Shadyside, Oakland, Downtown, the North Shore and, of course, the Strip District, where a good Saturday a.m. ramble is one of Pittsburgh's most unique pleasures.

Robert Ching, center, and Kathleen Narciso tend to customers at Moonlight Express, a vending station in the Strip District. Moonlight Express offers a variety of Asian dishes, including chicken and shrimp fried rice, pad thai and egg rolls. (Steve Mellon, Post-Gazette)

Squeezed into the Strip

Along Penn Avenue between 20th and 12th, plenty of restaurants advertise portable food, but real street foods are the items actually cooked or assembled before your eyes, on the sidewalk. The hot takeaway pepperoni rolls from Mancini's Bakery don't count. Neither does the warm, weighty bag of freshly roasted peanuts at Prestogeorge. Neither ware, though portable and tasty, is peddled from a cart, table or truck.

But the sizzling griddle outside Sam Bok grocery qualifies. Mung bean pancakes sizzle there, filling the air with a scallion-y scent. The pancakes are soft, almost custardy inside.

The egg rolls are pre-made and preheated, but if you order vegetable lo mein, the lone worker will toss a tangle of thin noodles and cabbage on the cooking surface; squirt a bit of hot sauce on it, and for $2 you've got one fast, hot, cheap lunch. There's always a line for the sticky chicken on a stick that smokes on the grill.

My dog likes nothing more than to pass by Wild River Kettle Korn, just across the street. There, in true hawker fashion, free samples are passed into palms from a long spoon, often dropping onto the sidewalk, within easy reach of quick canine jaws.

The huge black kettle and a waft of sugary smoke brings a bit of county fair charm to the Strip every Saturday, rain or shine, but you don't have to wait until summer fair season to taste the salty-sweet, crisp and hot corn.

At the corner of 20th and Penn, across from the flower market, is a little sausage-grilling cart where the difference is in the details. The smiling owner takes his culinary cues from Sunseri's, where sauce-laden sandwiches are assembled from quality Italian meats. Choose from his kielbasa, hot sausage or a hot dog. I chose hot sausage; rings of black olives scattered over the top were a nice, briny touch. Char-grilled banana peppers and strips of red bell add heat and sweetness, a thick tomato sauce adds tang and a sprinkle of provolone that melts within the neat aluminum wrapper mellows the whole.

In front of the building that once housed Alioto's Produce, Sam and Reinie roll open their giant meat truck. Slabs of barbecued ribs and long loins of meat hang from hooks above the heat, but the true triumphs of the truck are the sandwiches of shredded meat on chewy rolls. The pork roll is tangy and flavorful, built of meat that falls apart under the teeth. I am not a great lover of lamb, which has a sourish cast, but I can see why people love the Greek lamb sandwich in all its drippy, meaty, onion-spiked glory.

Watch, as the weather warms, for cherry lemonade on the sidewalk near Schorin. The Farmers at the Firehouse farmers' market starts up on May 15, and I've seen artisanal bakers and pizza makers there, hauling out impossibly hot stones and long spatulas, and young women folding freshly cooked farm-raised pork into hot sandwiches.

May is a bit early to see the vendors who seem to turn out for the social perks rather than the money, like Dilly's Ribs, where family members park around the booth in lawn chairs, inhaling the thick and spicy smoke.

And where, on a recent Saturday, was Lucy, my favorite banh mi maker? The brick wall outside the My Ngoc restaurant was bare without her little chair. On her beautifully light banh mi sandwiches French and Vietnamese cultures combine: Vietnamese sausage is topped with fresh vegetables and a pile of fresh cilantro on a warm, crusty baguette. It's the best sort of street food: specific, portable and gourmet.

Heart of Oakland

Nowhere are street vendors more depended upon than by student-populated Oakland, where the residents rarely cook, have little income, and any break from a university cafeteria is welcome. Mobile vendors service the University of Pittsburgh and Carnegie Mellon campuses morning, noon and night, part of the student lifestyle and campus culture.

It will be a tragedy when the lunch trucks at Schenley Plaza are booted when the area is turned into a park. It may happen soon: Gov. Rendell has earmarked $5 million of state capital funds to renovate the plaza. The truck food is inexpensive and surprisingly tasty; there is always a line to get it.

There is much to be savored on a bright day, sprawled out on that strip of sparse grass and peeling bark between Bigelow and the parking lot. There, a parade of diverse dishes was washed down with Thai iced tea, vegetable korma after basil chicken, a tangy tangle of papaya strands followed by minced chicken salad.

At the Kashmiri truck, there is a long menu as well as handwritten signs tacked up; the choice of curries, biryanis, stuffed breads, samosas and vegetarian entrees is intimidating. The line that snaked away from the truck, 10 people deep, was one-third Indian, and I took that as an endorsement for quality.

I was not disappointed, for the food was as good as many restaurants. Vegetable korma was laden with lima beans, chunks of carrot and potato. Aloo mattar was peas and potatoes suspended in a heady sauce; the peas popped on the tongue, the potatoes dissolved, having soaked up much of the spicy cooking liquid. The smaller-sized styrofoam entree container is enough: It's packed with food.

At Schenley Plaza, Thai cuisine represents. Nearer to Hillman Library, on the sidewalk, Thai Grill is a tiny white trailer with a less staggering list of choices. They do a decent soy-soaked basil chicken doused in soy and a delicious iced coffee. My brother, a student at Pitt, practically lives on the spicy basil chicken from the Namsai truck. The pad thai is cooked on the spot, loaded with egg, fresh sprouts and -- strangely -- broccoli. It's not as gummy as it could be. Namsai also prepares a few Chinese dishes: The General Tso chicken is sticky sweet and full of fresh broccoli.

The O'Cha truck is the travelling arm of the O'Cha restaurant in Verona. Here's where to get lighter Thai food. Som tam, a tangy papaya salad, was very fresh. Larb gai was rich minced chicken salad flavored with ginger and basil.

If none of these ethnic trucks floats your boat, cross the street to the corner of Bigelow and Forbes, and have "Scotty" call you "Dad" and fry you up a wienie on his little grill. He's been there since I was an undergrad and long before. Sometimes on weekends, he shows up in the little parklet named for Dan Marino in South Oakland, singing, flinging wienies, calling everyone by his favorite nickname.

Along Tech Road

At CMU, a row of little trucks climbs Tech Road. A few hundred yards off, there's scenic Flagstaff Hill, for sitting with food in your lap.

The difference at CMU's vendor scene is the falafel; I am amazed that there is only one outdoor falafel vendor in the entire city of Pittsburgh, as it's ubiquitous in other cities.

The Open Flame mobile unit takes its role seriously: Hours are posted outside the truck door, and it delivers on campus. The menu is an assortment of Middle Eastern specialties including gyros and falafel. The vegetarian platter contained a crisp salad of green peppers, tomato and lettuce. Two scoops -- of loose and creamy hummus and a very smoky baba gannouj -- are to be eaten with a warm half-pita. A dolma of rice bound in astringent grape leaves rounds out the experience.

Asian fare is represented by five trucks: Moonlight 3, Sree's, Little Bangkok, Thai Kitchen and Sunlite, which sells Chinese food. Moonlight 3 is a happy, sticker-covered truck selling everything from soda to coffee cake, and it is the only vendor city-wide selling pho, the glorious hangover-curing soup of the streets of Hanoi.

From Little Bangkok, we sampled a very salty scrambled basil tofu atop sticky rice. Out of curiosity, I tried the chocolate chip coffee cake from Moonlight 3, standard vending machine goods with a faintly metallic flavor and the texture of a brick. Sometimes it's better to skip breakfast.

Sree's serves an ever-changing roster of vegan and vegetarian South Indian food from a jaunty little red trailer; there are Sree's restaurant locations in Squirrel Hill and Sharpsburg, and a takeaway Downtown on the corner of Smithfield and Seventh Avenue. Sree's puts together a neat Indian wrap for the unique experience of eating palak paneer with your fingers. It's tasty, too.

North Side legends

One cannot discuss street food without mentioning Gus and Stella Kalaris, the king and queen of the cart. Or, rather, the grandfather and grandmother ("yia yia" is Greek for "grandmother") of the street vendors. They are Gus and Yia Yia of the orange cart with a striped umbrella parked on the shady side of West Ohio Street, near the tennis courts. They've been there forever, since "your dad was a lad," as the saying reads, though 1934 is long before my father was born.

Gus and Yia Yia's, as if you don't know, serves popcorn, peanuts, ice balls and nostalgia. Their prices haven't changed as long as I can remember -- maybe they never will. A bag of peanuts is $1. Popcorn -- butter drizzled on from a tiny oil can -- is $1. It's salty and hot. Ice balls, depending on size, are 75 cents, $1 or $1.50.

The balls are hand-scraped with a special shaving tool into little cups, then doused with the syrupy flavoring of your choice. I like root beer, but once I let Gus pick, and he gave me the North Side special: banana, orange and cherry. He told me that a guy comes and orders this every night, and the kids seem to like it. I liked it. It tasted of an icy cold childhood treat: Fruit Stripe gum.

Hot dog trail

The street hawker in cities across the United States and Europe glory in the sausage and the hot dog. My New york pal and I stopped by the hot dog cart on Walnut Street in Shadyside to watch a thin dog being fished from a pool of hot water. It was tossed on the grill for a quick char, wrapped in a soft bun and handed over. In New York, said New York, the bun would be roasted, and you wouldn't need to step to the back of the cart, to the condiment shelf, to squirt on the fixings yourself. In New York, it's all done to order.

That's the way it's done at Red Hot Pittsburgh, established in 2002 by two young guys, Alan and Rhett. Every day, on Grant Street near the Omni William Penn, they sell three kinds of Silver Star encased meat from their bright red, bullet-shaped cart until they run out. From 11 to 1:30-ish, the dog line stretches, 15 people deep, from the deep curb back into the shadow of the tall buildings.

For hot sausage, get there early. Otherwise, kielbasa is a hearty substitute.

The hot dogs have a good, beefy flavor and a bit of a snap to them. Prices are low: combos, which include a can of soda and a bag of Snyder's plain or barbecue chips, are $3 or $4.

People can get very emotional about their street vendor lunches. Violence nearly erupted when Red Hot ran out of red hots.

"Can't you put up a sign?" a disappointed customer growled, disgusted. Not when both hands are needed to wrap up hot dogs for a long line of hungry people.