# Connected Vehicles: Technology Review, State of the Art, Challenges and Opportunities
## 3 Applications  
The connected vehicle applications are designed and developed to address many of the current modern transportation issues [60]. In regards to the performance and implementation cost of these applications, they greatly depend on the design decisions such as real-time input sensor data, modes of communication used, location of the computation process, and secure data transmission [11,60]. The wide umbrella of connectivity is vehicle-to-everything (V2X), which secures the sharing of information seamlessly between the vehicle and everything in the right format at the right time. There are several potential applications for various forms of connectivity within the V2X paradigm, such as the following:  
* **Vehicle to occupant (driver/passenger) (V2O).** Enabling features like BLE/UWB-enabled phone-as-a-key; in-vehicle connectivity services for work, play, and commerce; driving error recognition and prediction; and QoX.  
Figure 2: VRU Collision warning, no-pass warning, and disabled-vehicle warning.  
* **Vehicle to vulnerable road users (V2 VRU).** VRUs include pedestrians/jaywalkers and cyclists as well as motor-cyclists and persons with disabilities or reduced mobility and orientation. V2 VRU can be an enabler for VRU detection, crossing intent and motion behavior recognition, and pre-crash warning.
* **Vehicle to vehicle (V2V).** Applications include post-crash warning, pre-crash warning, lane-change warning, cooperative collision warning, cooperative adaptive cruise control, visibility enhancement, wrong-way driver warning, intersection movement assistance, blind-spot warning, cooperative forward-collision warning, vehicle-based road-condition warning, communication relaying in case of emergency, smart cargo companions, last-mile delivery systems, fleet management systems, and self-organized autonomous vehicles.
* **Vehicle to environment (V2E)** includes road-condition monitoring, traffic-sign and light recognition, driving risk prediction, and perimeter monitoring systems.
* **Vehicle to infrastructure (V2I).** V2I is used for road-condition warning, SOS services, work-zone warning, do-not-pass warning, emergency vehicle signal preemption, intersection collision warning, in-vehicle amber alert, remote diagnostics and repair, pedestrian crossing information, red-light warning, pedestrian detection and warning, bicycle detection and warning, no left-hand turn warning, traffic condition monitoring, weather conditions, traffic light management systems, interaction management systems, parking management systems, and teleoperation in case of malfunctioning self-driving cars. For example, OnStar services provide automatic collision notification, enhanced roadside assistance, SOS emergency assistance, automatic diagnostic trouble code notifications, monthly vehicle health reports, service links, maintenance reminders, driving information, and on-demand diagnostics.
* **Vehicle to network (V2N).** V2N is used for disabled roadside vehicle warning, security credential management systems, multi-model mobility systems, dynamic on-demand mobility systems and services, cloud-based crowd-sensing services, real-time traffic monitoring, and for bringing attractive consumer experiences into the cabin to foster brand loyalty.  
In this section, we shed light on the safety and non-safety applications. However, mobility [61; 62] and environment applications [63; 64] also utilize the CV paradigm to provide many benefits including smooth traffic flow and eco-friendly road-trip decisions.