Evaluation of Speed, Flow, and Density Performance under Different Severity of Speed Bumps

Speed bumps are effective traffic calming tools that give transportation experts the ability to regulate vehicle speeds and enhance safety in particular areas. Despite being often utilized in populated areas, they are more common on other, busier roads (especially in developing nations), thanks to their efficiency, low cost of implementation, and simple installation procedure. Numerous speeds, flow, and density relationship hypothesized in various studies are supported by empirical data gathered in favorable circumstances. Because the graph is not a function, those who delved into comparison study under diverse situations frequently employ forced curves to demonstrate how flow and speed are related. However, the research makes an attempt to hypothesize that the behavior of dynamic speed-flow, speed-density, and flow-density functions is identical. In the study, the link between speed and flow under different severity speed bumps. The current study’s main objective is to is to quantify traffic volume and speed according to controlled conditions before comparing them to unfavorable speed bumps conditions of varying severity: low SB1, medium SB2, and high SB3. To determine the link between the traffic characteristics, the Greenshields model is used. The study show that decrease in speed from 66.6 km/h (control section speed) to 39.4 km/h, which is equivalent to a drop in speed of about 40%. SB2’s moderate severity bumps on traffic volume, speed, and density caused the flow rate to drop to 1236 vph and the free flow speed to drop to 28.2 km/h. While SB3’s high intensity bumps had an impact on traffic characteristics, the study show that the maximum value of speed is 5.34 (km/h), which equates to an hourly traffic flow of 816 cars.


Introduction
Speed bumps are vertical elevations in a road surface that are designed to incentivize vehicles to slow down and increase traffic safety.The existence of speed bumps may increase trip time and fuel consumption, generate traffic bottlenecks, delay emergency vehicles, also, when improperly signaled, result in vehicle damage or accidents.Yet, there are efficiency and safety issues with these impediments [1].Poorly built roads and the abuse of road safety measures to control traffic flow are factors that can make this challenging.Speed bumps are one of the crucial and frequently employed traffic stabilizing elements [2].For those that provide roads, they represent an additional maintenance and security expense [3].
The operational status of every particular traffic stream is characterized by three key variables: flow, speed, and density.While speed and flow are frequently used to gauge the quality of a road's service, density and flow are crucial for gauging quantity [4].You may figure out flow (q) by: q = n 3600 / T (1) Where: n = Numbers of automobiles have passed through a particular location in particular time interval (sec).q = equivalent volume per hour.It is possible to use the following generic formula to determine traffic flow, density, and space: Every variable in Eq. ( 2) also associate to a number of additional variables, such as the features of the route, the vehicle, the vehicle's owner, as well as outside factors like the weather (e.g.rainfall, wind).
In vehicles crashes, speed has been established as a major risk factor.It affects both the likelihood of an occurrence and the seriousness of the injuries brought on by collisions [5]- [8].The relationship between injury severity and speed is particularly problematic for bikers and pedestrians [9].According to research, pedestrians had a 90% likelihood of making it through a crash with a vehicle moving at 30 km/h or less, but only a 50% chance of avoiding collisions one at 45 km/h [10].Pedestrians, in particular, have nearly little chance of surviving a collision with a car driving at 80 km/h [11] .Vehicle speed controlling has thus become one of the primary strategies lead to lower the number of fatal traffic accidents [12] .Studied how speed hump affected the traffic making U-turns.He demonstrated how the construction of speed bumps clearly reduces the time that approaching traffic spends on the road.

Objectives
This study's main goal was to evaluate how speed bump characteristics affected on the speed, flow, density and the pavement condition.

Study area
Al-Madars Street located at AL-Shaab city is of the most important street in the city because its contain 6 schools, kindergarten and nursery school.Its length 1 kilometer and width 10 meters there are many bumps with different height located in front of the schools to provide safety for pedestrians by reduction the speed of vehicles.Figure 1 shows a satellite image for the street.

Figure 1. satellite image for the study area
In this study, traffic volumes were collected using the automatic count method (videotape) and converted to passenger car volume.There are three bumps on the roadway of our choice, but they are different heights (SB1 12.5mm, SB2 15.5mm, and SB3 17.5mm cm).The distances are SB1 to SB2 =260 meters, SB2 to SB3 =263 meters, The purpose of evaluating the separations between SB(speed bump) has to assess the tow potential effects of each on the anther.Simultaneously, the study accepted the measured average FFS of 90 km/h which is the design speed for a section.

Speed Bump and PCI
The speed bump is typically used in parking lots as a traffic-calming construction.The speed bumps typically measure 500 mm in length and 100 to 200 mm in height.Although it is not advised to use them on public roadways.These speed bumps are often constructed of recycled rubber and are intended to lower traffic speeds to 16 km/h.implementing [13].The inspector should operate the vehicle at its regular operating pace.Speed reductions near bump can be used to gauge severity; for low severity, these are notable, but no slower speeds are required for comfort or safety.For medium severity, the vehicle experiences significant vibrations, necessitating some speed reduction for comfort and safety.However, due to excessive vehicle vibrations, speed must be significantly reduced for comfort and safety, and the situation can be compared to a high severity of bumps.It uses a numerical rating system with a scale of 0 to 100. Figure 2 The pavement state is supposed to be in ideal condition at 100, and a failing part of pavement is represented by a score of 0. Based on the kind, severity, and amount of the observed distress, the PCI The computation It was thought that the pavement was in excellent condition.(PCI = 100) and deducting deduct values (DV).The relative weights provided by DV indicate the importance of the distresses and severity levels in connection to the pavement's performance.Table 1 lists Every sort of pavement deterioration for asphalt concrete (AC), along with its categories, degrees of severity, and measurement unit.3 Weathering/raveling (m 2 ) 3

Data Collection
Video recordings were used to acquire the data needed to estimate traffic flow.Figure 3 shows that using video recording to estimate speed is preferable to using the Bushnell Speedster III speed radar.The use of such a gadget produces more precise results when compared to speed estimation utilizing video records.The accuracy of the speed measurements supplied by the speed gun technology is 1 mile per hour [14].The current study used a smart phone technique additional to the conventional speed radar discussed earlier to assess the low speed.One way to calculate the velocity of a moving object, like a car, is by measuring the vertical distance between the observer and the object.

Impact of speed Bump Severity
Data on free flow speed and traffic volume were gathered for all four locations the control section, SB1, SB2, and SB3 in equal amounts.Speed-density and speed-flow models were using Greenshields models for drawn.

Analysis of Regression
Regression analysis was utilized in this section to model the link between PCI and the parameters of the speed bump (width, height and distance from preceding bump).The investigation considered a variety of independent variable mathematical forms (speed bump width, height and distance from preceding bump.The coefficient of determination (R 2 ) must be as high as it can be and significant at the 95% confidence level.The best model's coefficient of determination (R 2 ) is 0.9439 and is considered to be significant at a 95% confidence level because the significance of the (F) statistic is less than 0.001 as shown in Table 2.

Conclusion
There has been an increase in recent years in the significance of safety.Together with an increase in crashes and their severity, studies on highway traffic safety have multiplied.These studies included a section on the concept of traffic calming, which entails the use of both direct and indirect physical measures intended to slow down traffic and encourage ecologically friendly driving [15].The speed bump is one particular kind of traffic-calming structure.In order to force drivers to slow down, speed bumps were created using geometric roadway design elements [16].The current study, three types of severity of speed bumps were chosen SB1, SB2, and SB3 in addition to the control section in order to evaluate the outcome of speed bumps on traffic characteristics.This study's main goal was to evaluate how speed bump characteristics affected on the speed, flow, density and the pavement condition.Relationship between traffic density and speed in the control part of the Greenshields model.The study show that the speed decreased from 66.6 km/h (control section speed) to 39.4 km/h, which is equivalent to a speed drop of about 40%.SB2's moderate severity bumps on traffic volume, speed and density caused the flow rate to drop to 1236 vph and the free flow speed to drop to 28.2 km/h.While SB3's high intensity bumps had an impact on traffic characteristics, the studies show that the maximum speed is 5.34 (km/h), which equates to an hourly traffic flow of 816 cars.

Figure 3 .
Figure 3. Speed spot recorder and video recording Prior to beginning the field speed measurement, the standard speed gun (radar), smartphone, and actual car speed calibrations were made.The findings indicate that the smartphone technique could be used, particularly at speeds under 16 km/h.

Table 2 .
Model of speed bump characteristics on PCI