A dhaba is a roadside eating house serving a small fixed menu to truck drivers: dal, a seasonal vegetable, roti off a tandoor, curd, raw onion, and tea. Charpais outside instead of tables.
The economics are simple. Drivers stop where other drivers stop, food is cooked continuously, and turnover is high on thin margins. A driver eats and sleeps on the same charpai for the price of the meal.
The Grand Trunk Road dhabas between Delhi and Amritsar are an institution with their own reputations, and a handful, at Murthal and along the Punjab stretch, have become destinations in their own right for people who arrive by car.
Punjabi food as it is understood outside Punjab, tandoori, dal makhani, butter chicken, comes largely from this and from the refugee restaurants of Delhi, not from village kitchens.
The dhaba is also the only public building on a Punjab highway where a person with no money and nowhere to go can sit down for several hours and not be moved on.
The dhaba began as a stop for lorry drivers on the Grand Trunk Road: charpais outside, a tandoor, dal on a slow fire, and food served at any hour.
The menu is standardised across hundreds of kilometres and the quality is not. What is constant is the dal, the roti and the fact that the driver eats where the other drivers have stopped.
The city version is a restaurant imitating the road version. The road version is still there and is still where a driver from Ludhiana to Delhi actually eats.