Transportation and Safety Performance Functions - Essay Example

Transportation Transportation Transport can be defined as the movement of goods, services and/or people from one area to another. The transport system all over the world ensures that different communities and nations thrive with the exchange of goods and services offered. It gets to show one how an area develops. It has helped with the connection of people all around the world. Cultural diversification can largely be attributed to the transportation system (Kononov, 2003). Largely, the transportation system has contributed to the creation of jobs. Some of the jobs among the transport system include being engineers. Over the years, highway engineers have had to deal with the issues that arise from highway capacity. A manual, the first edition, was created to aid in the undisturbed flow, weaving sections, ramps and signalised intersections (Kononov, 2003). Introduction of new editions of the HCM has led to enhanced understanding of highway capacity with the publication of each HCM. 1944 was the year that saw the establishment of the Committee on Highway capacity. At present, the relationship between capacity, traffic volume, and the levels of service for the different types of highway facilities is at present, usually well understood. However, contrary to highway capacity, the relationship between physical characteristics of roads, safety and traffic volume is not fully understood. Usually, in the urban areas or environment, it is common to have problems when trying to remove or change the common beliefs of interchanges on safety and operations. There had not been any concern to produce a highway safety manual up until 1999. This document was expected to examine the accident by-product of commonly known road junctions and segments, for example, the freeways, two-lane roads, arterials among others. During an annual meeting organised by the TRB, it was concluded that, one of the main reasons for the lack of emphasis on safety was the absence of a single authoritative document that would be used to estimate the impacts on safety. Another meeting that acted as a follow-up to the previous one had researchers conclude that there was an apparent need to develop an HSM and recommended that the development work begin (Kononov, 2003). Though there has been an important, forward movement in the development of Highway Safety Manual (HSM), a lot has to done in places and areas of idea development and the solution of safety issues. The paper formally introduces the idea of Level of Service of Safety (LOSS) in the system of safety performance function (SPF) (Kononov, 2003). The introduction of the Level of Service of Safety will bring the needed agreement in the transport engineering profession. This in turn, will enable them to describe the degree of safety or unsafety of roadway segment; communicate effectively on the magnitude of safety problems to other top officials or other professionals in that field; provide a frame of reference for decision and implementation process and, a frame for reference from a safety perspective also to bring the illusion of road safety in all the areas involved. Only over the last decade has there been an established agreement among those who research on traffic that a non-Gaussian, non-linear relationship that exists between exposure to traffic and safety. The relationship is shown by the safety performance functions of various classes of intersections and roads (Kononov, 2003). In the statistical re-creation or re-making of traffic accidents, there is the assumption that the certain laws usually followed by the random variations or changes can be characterized or shown by a probability function. The use of a continuous distribution, for example, the normal distribution was the closest to a discrete or separate process. This is unlike, the Poisson distribution. This uses a more natural initial candidate distribution for the random separate and not so often events that usually take place. An HSM should provide a realistic estimate of expected accident frequency. The estimates are critical in the taking account of safety in highway planning and design. Safety Performance Functions are accident prediction models. They relate traffic exposure, to safety, measured in annual average daily traffic (AADT). The development of safety performance functions lends itself to the ideas and concepts of formulation of level of safety of service. The idea of LOSS uses qualitative measures that normally characterise the safety of a roadway portion in regard to its expected performance. Should the level of safety predicted by SPF represent and symbolize the expected number of accidents, then the degree of the deviation from the normal can be stratified or changed to represent specific levels of safety (Kononov, 2003). A gradual shift in the levels of change in the direction of the level of service of safety (LOSS) boundary line from the given representation shows that an increase in the number of accidents as AADT increases. The increase in road accidents is consistent with the Poisson error structure for the rural freeways. For most of the urban freeways, the negative binomial error structure reflects the over dispersion common for this type of environment. Safety problems that are present today are only described by the level of service of safety (LOSS) in magnitude (Kononov, 2003). The nature of any issue is decided through diagnostic study by direct identification and pattern recognition method. However, it is important to note that there are some normative parameters in the same safety performance functions that change with annual average daily traffic. In general, the extension and criticalness of the accidents gradually decreases and the distribution of accidents by accident types changes with the annual average daily traffic. Since LOSS provides an avenue for assessment of the extent of the safety issue, it is important to know that accident behaviours that may be influenced by correction may exist with or without being over represented in the total frequency as the safety performance functions has detected (Kononov, 2003). In conclusion, the development and creation of the safety performance functions (SPF’s) tends to lend itself to the formulation of the level of service of safety (LOSS). The idea of level of service uses qualitative measures that are typical of the safety of roadway segment and junctions in reference to its expected performance. There are four levels of service of safety that are proposed. These included; One, which shows a, low potential for accident reduction; two, that shows a better than the expected safety performance; three, which shows a less than expected safety performance and the fourth would show a high potential for accident reduction. Also, road safety should be said to be from the rate and the extent perspectives by using safety performance functions calibrated and marked for total accidents and fatality-only accidents (Kononov, 2003). References Kononov, J., & Allery, B. (2003). Transportation Research Record. Issue 1840 Transportation Research Record. National Research Council (U.S.). Transportation Research Board. Michigan: University of Michigan. Read More