Efficiency Enhancing Applications
There are several efficiency enhancing applications that use wireless communication technology in ITS to improve road and transportation efficiencies mainly by reducing congestions on roads and by easing traffic flow and reducing accidents. Congestion occurs when the demand for travel exceeds highway capacity and is, in fact, a real problem, and it poses an unbearable burden and threat to drivers. Several policies tackle the problem of congestion depending on local conditions and priorities, and one of them is to apply the Convenience or Cooperative Traffic Efficiency Application which is employed by authorities to ease traffic flow and resolve the problem of congestion. Cooperative Traffic Efficiency provides two applications:
1. Cooperative Speed Management (CSM)
2. Cooperative Navigation (CoNa)
1. Cooperative Speed Management comprises two services:
a. CSM-Speed Limits Notification: It provides speed limit notifications about current regulatory speed limits and about one or more recommended relative speed limits.
b. CSM-Traffic Light Optimal Speed Advisory: It is responsible for traffic light optimal speed advisory in which a roadside ITS station delivers information about the existing traffic light phases (green, yellow, or red), the time left before traffic light phase changes, and the duration for each phase. The vehicle adjusts its journey accordingly.
2. Cooperative Navigation
The Cooperative Navigation Application assists vehicles in navigation and aids vehicles in adjusting their itinerary according to their geographic location. The CoNa application provides many services, some of which are:
a. Traffic Probe (TP): in which vehicles collect TP information and send it to roadside units for traffic management.
b. Free-Flow Tolling (TOLL): When a car passes through a toll point, a roadside antenna connects with the OBU mounted in the car, and then vehicles are billed automatically as they pass through the tolling area, increasing throughput and reducing delay. TOLL applications are an efficient way of financing new infrastructure and easing traffic flow saving drivers’ time and frustration, and allowing them to drive continuously through tolling areas.
c. Vehicle registration, inspection, credentials: Vehicle inspection help to regulate the legality of goods/person transportations using wireless vehicular networks that allow the exchange of data between vehicles and infrastructures avoiding the need for stopping vehicles to validate a driver’s license, or to inspect vehicle or trip documentation.
d. Congested Road Notification (CRN): In which a vehicle sends notifications about road congestion to roadside units to help improve route and trip planning.
e. Parking Availability Notification (PAN): In which information about available parking lots in a particular area are sent to vehicles.
f. Parking Spot Locator (PSL): In which a vehicle obtains a list of available parking spots upon entering a parking lot .
Mobility Enhancing Applications
In the US, traffic congestion results in an $87.2 billion annual drain on the economy with road takers spending 4.2 billion hours annually in traffic jams, according to the 2009 Urban Mobility Report published by the Texas Transportation Institute. Wireless communications combine information from roadside units and in-vehicle devices to provide system managers and users with detailed real-time dynamic data about the conditions of the transportation system and the vehicles on the road helping them in making more efficient and convenient travel choices. In addition, wireless communications can provide information about weather and road conditions allowing drivers to make safer and more efficient decisions, and allowing the diversion of traffic away from an incident that may hinder the traffic flow. Consequently, this eases traffic flow and improves mobility on the roads .
Environmental Protection Applications
The implementation of wireless communications and ICT in the transport system allows road drivers to make choices that can affect both the overall demand for transport and for different transportation modes, such as easing home working, encouraging transportation mode switch, or optimizing the use of the system infrastructure in some way resulting in improved efficiency, improved safety, enhanced traveler experience or the use of a more sustainable mode of operation. Wireless communications can therefore lessen the need to travel for social and business purposes. In addition, since wireless communications connect corresponding sectors and services of the transport network through digital connections rather than the physical negotiation of geographical space, they can minimize the carbon intensive physical transport movement. Minimizing unnecessary travel using wireless communication and arranging well for unavoidable journeys using Real-Time Traffic Information (RTTI) is consistent with the “smarter choices” agenda. Smarter choices are ‘soft’ practices that affect travelers positively and boost a more sustainable voluntary behavior in schools, workplaces or at homes by producing and implementing travel plans. The smarter choices agenda could possible decrease national traffic levels by 10’15% if supplemented by ‘hard’ practices, and could thus significantly cut the carbon emissions of the transportation sector .
ITS advanced applications: Collision Avoidance Systems
Collision Avoidance Systems are another type of the applications of ITS that rely on several technologies including wireless vehicular communications. They have revolutionized transportation systems and roads by improving safety on roads, improving mobility and efficiency, and reducing the negative impact on the environment. The main advantage that would be gained from the installation and implementation of the collision avoidance systems on roads and in transportation is the almost complete reduction in the number of vehicles crashes and collisions. Consequently, collision avoidance systems would help increase, to a very high level, the safety levels on roads and as a result improve efficiency and mobility due to reduced congestions. Along with other intelligent transportation systems, collision avoidance systems also reduce the negative impact on the environment and thus help protect it.
I. Impact on Road Safety and Efficiency
Collision Avoidance Systems employ several techniques and applications that help avoid or minimize almost all different types of collisions. The following section provides a description of each type of collision along with the collision avoidance systems used to prevent it.
1. Rear-end collisions
Rear-end collisions occur when a vehicle collides into the vehicle in front of it when the rear vehicle cannot make a suitable maneuver to prevent the crash mainly because of following very closely the rear vehicle and sudden brake of the front vehicle. Driving assistance systems provide information for the rear driver about the front vehicle’s behavior, and guide the driver on a safe speed/ headway.
Collision Avoidance Systems used to prevent it
Rear-End Collision Avoidance Using Headway Monitoring
Monitoring vehicles’ headways allows for the application of rear-end collision avoidance systems which include:
1. Monitoring/informing systems: They monitor the driving environment, such as the headway with the front vehicle, and then inform the driver about it.
2. Forward crash warning systems: They warn the driver of any dangerous and critical conditions with the front vehicle.
3. Advisory systems: these advise the driver on the most suitable control actions that should be taken to maintain safety.
4. Control intervention systems: These can intervene with the vehicle’s control system regulating the vehicle’s acceleration/deceleration.
Rear-End Collision Avoidance Using Wireless Networks
Rear-end collisions can also be prevented or minimized in severity, by decreasing the time between an emergency event happening and the time that approaching vehicles react to it. There are several methods by which this can be achieved but the most common is through the use of wireless communication to broadcast warning messages to approaching cars. The warning messages sent by a braking or a slowly moving vehicle enables the approaching vehicles to take appropriate actions, such as by slowing down or changing lanes, much earlier than it is possible with the current use of visible light signals; therefore, reducing the possibility of crashes and chain collisions.
2. Chain collision accidents
Chain collision accidents occur when an initial collision between two vehicles results in a series of collisions involving the vehicles behind. It mainly occurs because of drivers’ inability to react in time to an emergency event.
Collision Avoidance Systems Used to prevent it
Chain collisions are usually avoided using a Car Collision Avoidance (CCA) mechanism in which an incident warning message is propagated from vehicle to vehicle allowing drivers to respond to a critical incident before actually seeing it. This allows avoiding the traditional chain of drivers reacting to the brake lights of vehicles ahead of them, thus reducing the time delay between the occurrences of a critical incident and approaching vehicles being informed of it. This mechanism usually relies on wireless communications in which vehicles transmit warning messages to each other alerting the vehicles and the drivers to take proper action either by slowing down to a recommended speed or by applying a higher than normal deceleration rate
3. Lane change and overtaking collisions
Lane change takes place when a vehicle changes its position from an originating lane to a destination lane of the same traffic direction. Overtaking happens when vehicles change position on lanes of opposite traffic direction, such as overtaking a slow moving truck on a divided two-way highway.
Collision Avoidance Systems used to prevent it
Lane change and overtaking collisions can be avoided by two measures: infrastructural and in-vehicle. Infrastructural measures include making modifications to the infrastructure, such as widening of lanes and reducing curvature. On the other hand, in-vehicle driver assistance systems provide information to the drivers about the surrounding traffic conditions, using sensors and wireless communication networks, allowing the drivers to take proper actions to avoid lane change and overtaking collisions. In-vehicle driver assistance systems include:
a. Driver informing systems: continuously inform the drivers about the driving environment and conditions, especially those that are not perceivable to the drivers (e.g. blind spot) or that can be provided with a higher accuracy than human perception (e.g. vehicle speed).
b. Driver warning/advisory systems: evaluate the safety of a situation and warns the drivers when a particular threshold condition is met or exceeded. It can also provide advice to the drivers about the optimal actions to take, such as the optimal moment to overtake.
c. Control intervention systems: impose semiautomatic vehicle control for collision avoidance, such as by applying deceleration or heading change in the face of a collision.
d. Fully automatic control systems: impose automatic vehicle control from braking, to steering and throttle control in the face of a collision, without allowing the driver to overrule the system’s actions.
4. Intersection Collisions
A large portion of road accidents occur at road intersections, and they can involve pedestrians as well as vehicles. Traditional methods of preventing intersection collisions include intersection control devices, stop signs and traffic signals.
Collision Avoidance Systems used to prevent it
There are several collision avoidance systems that are used to prevent intersection collisions and thus improve safety and efficiency on the roads, some of which include:
a. Cooperative systems: create a connected network between vehicles and the infrastructure based on vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) wireless communications which form the core of such systems and can help drivers understand the complex state of activities occurring in an approaching intersection.
b. Intersection Control Devices: work in agreement with the basic traffic laws to help provide information to drivers so they can drive their vehicles safely along the road. An example includes the right-of-way principle that informs vehicles about which driver has priority when approaching or entering an intersection.
c. Autonomous Collision Avoidance (CAS) Systems: These systems mainly use image processing algorithms to recognize objects on roads and then track them to estimate their dynamics and alert drivers of possible collisions. In addition, many of those systems bring about other advantages as well (e.g. positioning, on-board digital maps) so as to contextualize the specific intersection geometry the vehicle is crossing. These systems have attracted particular attention of researchers as low-cost computers increased in performance allowing for increased road efficiency and lower costs.
Other Avoidance Techniques
Some other collision avoidance systems use stereo infrared vehicle-mounted cameras to track the movements of pedestrians at night and then provide a voice warning and highlight infrared images of the pedestrians using a heads-up display on the windshield. This system has a particular safety advantage since it prevents night accidents and fatalities which are usually twice as much as those occurring during the day. Other systems of the same type depart from the traditional vehicle-mounted cameras and use several video cameras installed at an intersection to predict possible collisions.
5. Car and Pedestrian Collisions
Car and Pedestrian collisions are considered the most serious road accidents as they usually lead to fatalities or serious injuries. However, during the last decades the number of fatalities or serious injuries from car and pedestrian collisions has declined due to advancements in passive vehicle safety by the use of safety belts, airbags, the Antilock Braking System (ABS), crumple zones, and the electronic stability control (ESC(. Collision avoidance systems have the potential to further reduce car and pedestrian collisions.
Collision Avoidance Systems used to prevent it
The implementation of new vehicle-to-vehicle and vehicle-to-infrastructure wireless communications in the collision avoidance systems and exchanging information about danger zones can enhance the safety of car passengers by avoiding collisions. Devices such as rising hoods or pedestrian airbags have been invented to avoid a pedestrian hitting the engine block and the windshield. In addition to the implementation of active collision avoidance systems, governments worldwide are setting new requirements and enacting new laws to increase pedestrian safety.
Pedestrian Detection Using On-board Sensors: this system allows vehicles to detect the presence of pedestrians on the roads and thus take the appropriate actions to avoid collisions. Some of the sensors used in this system include: Camera-Based Systems that capture the Visible Spectrum, Cameras that capture the Infrared Light Spectrum, Laser Scanner Devices, Radars, and Sensor Fusion .
II- Impact on Mobility
In addition to improving safety and efficiency on roads, collision avoidance systems also improve the mobility of vehicles allowing for vehicles to move freely without having to go through congested traffic and also allows for fast emergency responses. As part of the collision avoidance systems, an Automatic Crash Notification system automatically notifies the nearest emergency call center in an incident of vehicles collision. After that, data from vehicular sensors will provide the call center with all the information needed to save the situation, such as: whether the vehicle was involved in a crash; whether an airbag was activated; the physical impact to the vehicle; whether the vehicle did roll-over; the history of vehicle deceleration and status; the number of car passengers, etc. This advanced automatic crash notification system allows for the severity of emergency situations and their precise locations to be determined, and can thus save lives readily while exploiting rescue resources efficiently and sustainably. This method is certainly more efficient, less time-consuming and greatly improves mobility rather than the old method of accident notification in which a witness of the collision calls the police and the police then connect with the fire department and medical services calling for an ambulance to the collision site .
III- Impact on Environmental Performance
In addition to directly improving traffic management and easing traffic flow through the transmission and processing of information, all of the different collision avoidance systems described above help avoid excessive and aggressive driving maneuvers, uneven driving pace and unsafe speeds/ headways, sudden stopping and starting, and unnecessary speeding and lazing. These result in ecological driving or “eco-driving” which refers to good general operation of a vehicle to optimize performance and reduce environmental impact. The use of wireless communications and ICT in collision avoidance systems can further support greater automation and mobility within the transport system and therefore provide a further step towards reducing carbon emissions and reducing the carbon footprint of vehicles, for example through intelligent speed adaptation. Moreover, the implementation of the collision avoidance systems help reduce traffic congestions and unnecessary starting and stopping further reducing carbon emissions .
Collision avoidance systems result in changes in mean traffic speed per unit time, reduction in the period of the episode of reduced capacity, reduction in unnecessary sudden stops and starts, reduction of unnecessary vehicle-miles traveled (VMT), and reduction in traffic congestion which result in a total reduction of dangerous vehicle emissions and reduction in fuel consumption. Some of the impacts of those changes include:
1. Reduction in the emissions of Nitrogen Oxide (NOx).
2. Reduction in the emissions of Volatile Organic Compounds (VOC).
3. Reduction in the emissions of Carbon Monoxide (CO).
4. Reduction in fuel consumption .
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