You are presented with multiple paper abstracts, alongside the associated literature review and chapter titles. Given the provided information, you are going to do a literature review. Please generate a coherent literature review that synthesizes the content, draws connections between different works, highlights major findings, and identifies any gaps in the existing research.

Literature Review Title: Pedestrian Protection Systems: Issues, Survey, and Challenges 
Chapter Title:  A. Infrastructure Design Enhancements 
1. Abstract of Cited Paper (BIB001):  We provide a brief critical review and assessment of engineering modifications to the built environment that can reduce the risk of pedestrian injuries. In our review, we used the Transportation Research Information Services database to conduct a search for studies on engineering countermeasures documented in the scientific literature. We classified countermeasures into 3 categories-speed control, separation of pedestrians from vehicles, and measures that increase the visibility and conspicuity of pedestrians. We determined the measures and settings with the greatest potential for crash prevention. Our review, which emphasized inclusion of studies with adequate methodological designs, showed that modification of the built environment can substantially reduce the risk of pedestrian-vehicle crashes. 
2. Abstract of Cited Paper (BIB002):  Deciding where to mark crosswalks is only one consideration in selecting appropriate solutions to improve pedestrian safety and access. Five years of pedestrian crashes at 1,000 marked crosswalks and 1,000 matched unmarked comparison sites were analyzed. More substantial improvements were recommended to provide for safer pedestrian crossings. Language: en 
3. Abstract of Cited Paper (BIB003):  The U.S. Federal Highway Administration (FHWA) has made improved pedestrian safety a priority and seeks to achieve a 10% reduction in pedestrian fatalities by 2007. Research staff from the FHWA Office of Safety Research and Development at the Turner-Fairbank Highway Research Center are investigating new ways to help reach this goal. Among the research topics under study is evaluation of countermeasures to improve safety in pedestrian crossings that are not controlled by traffic signals. This includes in-roadway warning lights in which each side of a crosswalk is lined with a series of amber lights embedded in the roadway that face oncoming traffic. The lights are visible to approaching drivers as a warning that a pedestrian is in or near the marked crosswalk. This article describes an FHWA study that examined pedestrian and driver behavior at crosswalks in Alexandria, Virginia, during daylight and dark conditions over the course of 1 year. Further evaluations will be conducted immediately before, immediately after, and 1 year after in-roadway warning lights are installed.

Literature Review:
Infrastructure enhancements to reduce pedestrian-related accidents can be divided into three categories of countermeasures: speed control, pedestrian-vehicle separation, and measures to increase visibility and conspicuity of pedestrians BIB002 . Reduction of speed results in fewer injuries due to the lowering of kinetic energy as well as greater reaction time (Fig. 1) . The techniques for speed control include single-lane roundabouts, speed bumps, pedestrian refuge islands, and use of multiway stop signs BIB002 . Separation of pedestrians and vehicles can be performed by measures such as installing traffic signals, allocating exclusive time for pedestrian signals, in-pavement flashing lights to warn drivers, and automatic pedestrian detection at walking signals. Pedestrian visibility can be increased by improving roadway lighting, since a majority of pedestrian fatalities occur at night time. Since parked vehicles block the vision of drivers as well as pedestrians, removing on-street parking and implementing diagonal parking in residential streets would help in reducing accidents, especially those involving children. In BIB002 , limited studies have been conducted on the effects of these measures, showing that more evaluations are required. In BIB003 , experiments comparing marked and unmarked intersections for pedestrian safety are described. For single-lane or low-density roads, there has been no significant difference between fatality rates on marked and unmarked intersections. However, multilane marked crosswalks with average daily traffic greater than around 10 000 have been observed to have greater rate of accidents than the unmarked ones, particularly for multilane crossings. A possible explanation given by them is that multilane roads with heavy traffic at high speeds are difficult to cross for many pedestrians. In such cases, the presence of marked crosswalks may be encouraging people to cross there instead of using a signal-controlled intersection, therefore increasing the number of at-risk pedestrians, particularly children and the elderly. They propose that marking intersections should be used in conjunction with other measures described above in order to increase safety. In BIB001 , a similar conclusion is arrived at in experiments with older pedestrians. FHWA in BIB004 proposes flashing light warnings on pedestrian crosswalks in order to warn the drivers of the presence of pedestrians. These lights can be triggered by a button pressed by the pedestrian or an automatic detection system. Such systems are being tested on selected intersections in Virginia. In  , the seriousness of the accidents involving VRUs in India is discussed. The solutions proposed include putting regulators on buses, trucks, and other heavy vehicles to limit their speed, segregation of fast and slow traffic, providing safe walking and road crossing facilities, and traffic calming measures such as the use of roundabouts. Measures necessary in urban areas as well as those on highways and rural roads are specifically addressed.