There are many reasons why unsanctioned urban street racing is extremely dangerous, including:
Young or inexperienced drivers: Often the competitors involved in an urban street race are younger, less experienced drivers.
Alcohol or drugs may be involved: Many drivers engaged in these races are also be impaired by drugs or alcohol at the time of the race.
Reckless behavior: Whether the drivers are impaired by other substances or not, this type of activity increases adrenalin and increases the risk of more reckless behavior.
High-speed driving: The faster a driver goes, the greater the risk he or she has of losing control of the vehicle. Speeding also makes it harder to stop if the driver encounters an unexpected hazard, such as an animal in the road or pedestrian crossing the street.
Ignoring/violating traffic laws: Drivers may run a red light, ignore a stop sign or fail to acknowledge a designated crossing area.
Rain or other inclement weather: Any type of bad weather can impact how a vehicle reacts. Rain, for instance can cause a vehicle to hydroplane, while hitting a patch of ice could cause a car to spin out and crash.
The very nature of urban street racing incites more aggressive behavior, increasing the likelihood of a collision, as well as road rage and other violent behaviors. Unfortunately, these incidents often injure, kill or maim innocent bystanders.