Stray dogs are domesticated dogs that lived with people at some point, usually as pets. They have either been abandoned or accidentally released into urban areas, and now fend for themselves. These dogs' offspring are also considered as strays, so the term "stray" may be applied to many generations removed from the original stray founder(s).

The size of stray dog populations always corresponds to the size and character of the human population of the area. Urban features which create and sustain stray dog populations:

1) Large amounts of exposed garbage, which provide an abundant source of food
2) A population of slum and street-dwellers, who often keep the dogs as free-roaming pets, like in India.

Some problems caused by stray dogs: Rabies can be a fatal disease which can be transmitted to humans. Although all warm-blooded animals can get and transmit rabies, dogs are one the most common carriers. Dog bites can occur when dogs are trying to mate or fighting among themselves. Pedestrians and other humans in the vicinity may be bitten by the fighting dogs. Females with pups are often protective and may bite people who approach their litter. Barking and howling is an accompaniment to dog fights which invariably take place over mating. Urine smell is an unsavory product of territory marking.

Some of the stray dogs in Bucharest are seen crossing the large streets at pedestrian crosswalks. The dogs have probably noticed that when humans cross streets at such markings, cars tend to stop.

See also: https://en.wikipedia.org/wiki/Free-ranging_urban_dog

Source: Wikipedia (All text is available under the terms of the GNU Free Documentation License and Creative Commons Attribution-ShareAlike License.)