Pedestrian Protection Systems: Issues, Survey, and Challenges <s> C. Active Safety Systems Based on Pedestrian Detection <s> An approach to robot perception and world modeling that uses a probabilistic tesselated representation of spatial information called the occupancy grid is reviewed. The occupancy grid is a multidimensional random field that maintains stochastic estimates of the occupancy state of the cells in a spatial lattice. To construct a sensor-derived map of the robot's world, the cell state estimates are obtained by interpreting the incoming range readings using probabilistic sensor models. Bayesian estimation procedures allow the incremental updating of the occupancy grid, using readings taken from several sensors over multiple points of view. The use of occupancy grids from mapping and for navigation is examined. Operations on occupancy grids and extensions of the occupancy grid framework are briefly considered. > <s> BIB001 </s> Pedestrian Protection Systems: Issues, Survey, and Challenges <s> C. Active Safety Systems Based on Pedestrian Detection <s> Warning systems are being developed for left-turning vehicles at intersections where protected left-turns are not warranted or cannot be provided, based on limitations of right of way or intersection capacity. These are meant to provide warnings to left-turning vehicles of vehicles approaching from the opposite direction, when the time to turn may be deemed unsafe. To implement these warning systems, it is necessary to estimate in near real time, the probability of conflict between the two approaching vehicles. A study is being conducted with the help of video and radar at various intersections, to obtain estimates of turning time and acceptable gaps for drivers under various situations. Initial pilot observations indicate that the presence of pedestrians in intersections had an immediate and substantial impact on movement of left turning vehicles. From a preliminary systematic video analysis of the intersection, in the presence of pedestrians on the destination crosswalk, the mean and standard deviation of both the gap and gap components (i.e., turning time and the “buffer” between the turning vehicle and the next oncoming vehicle) increased. On the basis of these observations, pedestrian-detection mechanisms may be useful in such intersection warning systems, with a threshold for warning that is adjusted for pedestrians when they are present or in the vicinity of the destination crosswalk. <s> BIB002 </s> Pedestrian Protection Systems: Issues, Survey, and Challenges <s> C. Active Safety Systems Based on Pedestrian Detection <s> Pedestrian safety is a primary traffic issue in urban environment. The use of modern sensing technologies to improve pedestrian safety has remained an active research topic for years. A variety of sensing technologies have been developed for pedestrian detection. The application of pedestrian detection on transit vehicle platforms is desirable and feasible in the near future. In this paper, potential sensing technologies are first reviewed for their advantages and limitations. Several sensors are then chosen for further experimental testing and evaluation. A reliable sensing system will require a combination of multiple sensors to deal with near-range in stationary conditions and longer-range detection in moving conditions. An approach of vehicle-infrastructure integrated solution is suggested for the pedestrian detection in transit bus application. <s> BIB003 </s> Pedestrian Protection Systems: Issues, Survey, and Challenges <s> C. Active Safety Systems Based on Pedestrian Detection <s> Intersection collision warning systems can potentially reduce the number of collisions and associated losses. A critical design aspect of these systems is the selection of warning criteria, which represent a set of conditions and parameters under which the decision and the timing to issue warnings are determined. Proper warning criteria allow the generation of timely signals for drivers while minimizing false and nuisance alarms. The paper describes the development of a methodology to observe and analyze the selection of time gaps exhibited by driver behaviors in a real-world setting. The data collection procedures and analysis techniques are explained for left-turn across-path-opposite-direction scenarios, which constitute more than a quarter of crossing path crashes at intersections. Exemplar data sets from an urban, signalized intersection are used to illustrate methods of deriving time gap acceptance behaviors. The extracted information can serve as the basis for selecting gap acceptance thresholds in warning criteria, and the demonstrated methodology can be applied in the development of intersection collision warning systems. <s> BIB004 </s> Pedestrian Protection Systems: Issues, Survey, and Challenges <s> C. Active Safety Systems Based on Pedestrian Detection <s> Cooperative Intersection Collision Avoidance Systems (CICAS) are likely to be among the first and most quality-of-service-critical users of wireless DSRC communications. Vehicle and infrastructure systems need to exchange data about the state of the intersection with high reliability and low latency. This paper estimates the number of vehicles that would need to share the DSRC safety communication channel at an intersection under worst-case conditions in rural, suburban and urban environments, to provide a starting point for defining the capacity that wireless channel needs to provide in order to support CICAS services. <s> BIB005 </s> Pedestrian Protection Systems: Issues, Survey, and Challenges <s> C. Active Safety Systems Based on Pedestrian Detection <s> Awareness of what surrounds a vehicle directly affects the safe driving and maneuvering of an automobile. This paper focuses on the capture of vehicle surroundings using video inputs. Surround information or maps can help in studies of driver behavior as well as provide critical input in the development of effective driver assistance systems. A survey of literature related to surround analysis is presented, emphasizing detecting objects such as vehicles, pedestrians, and other obstacles. Omni cameras, which give a panoramic view of the surroundings, can be useful for visualizing and analyzing the nearby surroundings of the vehicle. The concept of Dynamic Panoramic Surround (DPS) map that shows the nearby surroundings of the vehicle and detects the objects of importance on the road is introduced. A novel approach for synthesizing the DPS using stereo and motion analysis of video images from a pair of omni cameras on the vehicle is developed. Successful generation of the DPS in experimental runs on an instrumented vehicle test bed is demonstrated. These experiments prove the basic feasibility and show promise of omni-camera-based DPS capture algorithm to provide useful semantic descriptors of the state of moving vehicles and obstacles in the vicinity of a vehicle <s> BIB006
Considerable research is being conducted by various groups for designing pedestrian detection systems. Such systems can employ various types of sensors and computer vision algorithms in order to detect pedestrians and to predict the possibility of collisions. The output of the systems can be used to generate appropriate warnings for the driver or to perform autonomous braking or maneuvering in the case of an imminent collision. Vehicle-mounted sensors are useful in detecting pedestrians and other objects on the road. However, visibility from the vehicle is limited. It is often the case that it is difficult or impossible to observe the dangerous object from the vehicle itself. Hence, it is useful to have systems with sensors in the infrastructure, which would perform monitoring of traffic and send appropriate signals to the vehicle through wireless communication channels. However, since mounting infrastructure is expensive, such systems would be useful for specific places such as busy and dangerous intersections, school areas, and blind curves. Infrastructure-based systems are particularly useful for transit buses that make frequent stops at designated bus stops with a large concentration of pedestrians. Such systems can monitor the pedestrians near bus stops and intersections along the bus routes and send warnings to the bus drivers in case of dangerous situations. Various sensors and approaches that are used for pedestrian detection for transit bus applications are discussed in BIB003 . An integrated vehicle-infrastructure system is proposed for pedestrian protection that uses wireless communications. The European project PUVAME proposes an infrastructurebased solution to prevent collisions between VRUs and transit buses. They use off-board cameras that observe intersections and bus stops to track the movement of buses as well as VRUs. Occupancy grids BIB001 over the ground plane are used to integrate several sensors in the same probabilistic framework. The risk of collision is computed based on the time to closest approach and the closest point of approach. Pedestrian crossings at unprotected left turns are a serious cause of accidents. On such turns, the drivers turning left are supposed to yield to the vehicles approaching from opposite directions as well as the crossing pedestrians. In BIB002 , the design of a system is proposed that detects these conflicts and warns the left-turning driver if there is insufficient time to make the turn. It is observed BIB004 that the presence of pedestrians produces significant increase on turning time as well as buffer with oncoming vehicles. Thus, it is helpful to complement the warning system with an infrastructure-based pedestrian detection system in order to adjust the warning thresholds when pedestrians are present. In countries such as India and China, there has recently been a large amount of road construction and other transportation infrastructure. There is an urgent need to develop infrastructurebased solutions in these roads, since it would be easier and more efficient to build these systems along with the roads rather than to retrofit them at a later stage. For effective enhancement of driver safety, vehicle as well as infrastructure-based system should have the perception of complete surroundings, including the events taking place in the front, back, and sides of the car. In BIB006 , the importance of such a "Dynamic Panoramic Surround" (DPS) map is emphasized, and a novel approach for generating the DPS using a pair of omnidirectional cameras on the vehicle is proposed. The technical report BIB005 for California PATH program has defined a similar concept for infrastructure-based systems, which is called the Dynamic State Map, which plots the dynamic information at the intersection, including the traffic signal state, vehicles approaching the intersection, and local environmental conditions. They discuss the communications requirements in three scenarios: 1) rural intersection with low-density highspeed traffic; 2) suburban intersection at high-speed arterials; and 3) high-density low-speed gridlocked urban intersection. Thus, it is seen that pedestrian safety can be improved using a variety of approaches. Infrastructure enhancements can be employed at selected places where there is high incidence of pedestrian accidents. Vehicle body modifications could be enforced by the government to improve pedestrian safety. The sensor-based vehicle systems may be initially introduced in luxury vehicles and, once the technology becomes affordable, could be mandated by the Government. Infrastructure-based sensors and detection systems can be deployed in dangerous zones. They could communicate with the vehicle-based systems so that the vehicles can obtain a complete picture of the scene and make proper judgments. In the following sections, we focus on the research conducted in vehicle and infrastructure-based systems for pedestrian detection. 