Yes, there are systems that provide crash warnings for connected vehicles. These systems use vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communication to exchange information about the vehicle's location, speed, and direction of travel. This information can be used to alert drivers to potential hazards, such as other vehicles that are braking suddenly or stopped abruptly.

One example of a crash warning system is the Dedicated Short-Range Communications (DSRC) system, which is being developed by the National Highway Traffic Safety Administration (NHTSA). DSRC uses a 5.9 GHz band to exchange information between vehicles and roadside infrastructure. The system can provide alerts to drivers about upcoming hazards, such as traffic congestion, weather conditions, and construction zones.

Another example of a crash warning system is the Cellular Vehicle-to-Everything (C-V2X) system, which is being developed by the 3GPP standards organization. C-V2X uses a cellular network to exchange information between vehicles and roadside infrastructure. The system can provide alerts to drivers about upcoming hazards, as well as enable self-driving vehicles to communicate with each other.

These crash warning systems are designed to improve road safety by reducing the risk of accidents. By providing drivers with early warning of potential hazards, these systems can help them to take evasive action and avoid collisions.