# Traffic System: Civil Engineer

Mediarilisnusantara.com – Before understanding the value of design, a civil engineer must understand the functions, operations, and elements of a functioning traffic system. According to Roger P. Rosess, et al 2011, there are five important components that interact with each other in the traffic system, including road users-drivers, pedestrians, bicyclists, and passengers, vehicles-private and commercial, street and highways, traffic control devices, and the general environment.

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This essay can be discussing the meaning of the relationship between the design values ​​obtained from the 85th and 15th percentiles for the five components of the traffic system. In designing traffic engineering, it will be simple if the components of the traffic system have uniform characteristics, and road users have exactly the same reaction actions so as to enable a greater level of safety. Of course in reality the system does not work uniformly so simple subjects such as reaction time, visual characteristics, and walking speed become complex and need to be taken into account.

One of the most commonly used static distributions in determining design values is the normal distribution. According to Evi Noor Diana 2016, the normal distribution is a continuity distribution with the probability that the data around the objectives and graph functions can be described as bell-shaped or bell-shaped. For example, the number of walking humans has a normal walking speed distribution between 3.0 and 5.0 fi/s.

Based on the explanation of the normal distribution and the examples given, it is possible to analyze the meaning of the 85th and 15th percentiles. This means that in the normal distribution diagram the 85th percentile is the number of people who have a walking speed of more than 3.0 and 5.0 fi/s while the 15th percentile is the number of people who have a speed of less than 3.0 and 5.0 fi. /s.

Based on the explanation that has been given, this percentile can be applied in designing traffic systems. As an example of the application of the normal distribution there are designing a traffic signal system for pedestrians and vehicles. To account for these two components, the 85th and 15th percentiles are applied to different operations. The 15th percentile is used to calculate the length of the red light to cross the road, while the 85th percentile is used to estimate the reaction of vehicle users when the red light begins.

The 15th percentile plays an important role in determining the length of the red light to support the safety of pedestrians who have speeds slower than the same as 3.0 and 5.0 fi/s. Meanwhile, the 85th percentile plays a role in determining the fastest reaction of vehicle users to the reaction of pedestrians who have speeds of more than 3.0 fi/s and 5.0 fi/s to red lights.

Reference

Noor Diana, Evi, 2016. A BAYESIAN APPROACH TO LOG-NORMAL PARAMETER ESTIMATION FOR NON-INFORMATIVE PRIOR. Page – 6.

2011. Roess Roger, S. Prassas Elena, R. McShane, Willian, 2011. Traffic Engineering Fourth Edition.