A THEORETICAL OVERVIEW OF ROAD HUMP EFFECTS ON TRAFFIC SPEED IN RESIDENTIAL ENVIRONMENTS <s> Related Literature on Effects of Road Hump Design <s> Traffic calming measures are used to reduce speeds and consequently accidents. The original work on speed reducing road humps was carried out at TRL in the early 1970's and was based on circular profile (round top) road humps of various dimensions. More recently, in order to improve the advice to Local Highway Authorities in Great Britain, the Driver Information and the Traffic Management Division of the Department of the Environment, Transport and the Regions has commissioned TRL to assess the effectiveness of a wide range of physical traffic calming measures used on the public roads. The work has included measures involving vertical deflections (round-top humps, flat-top humps, thumps and lower height humps, speed cushions, sinusoidal humps and 'H' and 'S' humps) and horizontal deflections (single lane working and two way chicanes). This paper summarises the results that have been obtained by TRL from a number of different test track trials and public road studies of urban traffic calming measures during the past six years. It briefly describes the different measures and considers how changes in the dimensions, layout and spacing of the measures affect vehicle speeds. It also considers the effect of the measures on driver behaviour, passenger discomfort, traffic flows and accidents. Public reaction to traffic calming measures is included as well as the likely impact of the measures on vehicle generated noise, ground-borne vibration and vehicle exhaust emissions. For the covering abstract, see IRRD E101115. <s> BIB001 </s> A THEORETICAL OVERVIEW OF ROAD HUMP EFFECTS ON TRAFFIC SPEED IN RESIDENTIAL ENVIRONMENTS <s> Related Literature on Effects of Road Hump Design <s> The best way to influence drivers speed is through traffic calming measures. The best way to influence crossing speed over a road hump is through the discomfort that drivers experience when crossing. There is a great variety of road humps used today but in fact, an ideal road hump could replace them all. This ideal road hump would be comfortable to cross at low speed but discomfort would increase rapidly with speed above 20 km/h. The purpose of this thesis is to study how physical identities of road humps such as length, height, length of ramps etc, affect driving comfort and crossing speed. Vertical acceleration has often been used to describe the comfort of road humps. To study the connection between physical identities, vertical acceleration and crossing speed, different measurements were conducted. Vertical acceleration was measured with a specially instrumented vehicle, speed was measured with a radar gun and physical identities were measured with a total station. One of the main conclusions from this thesis is that each and every road hump has a special connection between vertical acceleration and crossing speed that is unique. Another conclusion is that there can be a conflict between driving comfort and crossing speed. If one physical identity is changed to increase or decrease vertical acceleration, it can have the unwanted effect that crossing speed would increase. It is therefore important to be aware of this possible conflict when designing road humps. (A) This document is also available electronically via Internet at URL: http://www.tft.lth.se/publ/5000/Thesis125SBscr.pdf <s> BIB002 </s> A THEORETICAL OVERVIEW OF ROAD HUMP EFFECTS ON TRAFFIC SPEED IN RESIDENTIAL ENVIRONMENTS <s> Related Literature on Effects of Road Hump Design <s> PROBLEM ::: The effectiveness of speed humps, 14 ft (4.3 m) wide by 3.5 in (8.9 cm) high, and tables, 22 ft (6.7 m) wide, on 12 streets in Salt Lake City, Utah was investigated. Mean and 85th percentile spot speeds, speed limit compliance, motor-vehicle crashes, and resident opinions were considered. ::: ::: ::: METHOD ::: Spot speeds were collected at 18 "between-hump" locations. Motor-vehicle crash data were obtained for "before" and "after" periods of equal duration. A total of 436 residents were surveyed; 184 responded. ::: ::: ::: RESULTS ::: The mean and 85th percentile speeds decreased at 14 and 15 locations, respectively. The average reduction in the 85th percentile speed (3.4 mph or 5.4 km/h) was significant in flat and rolling terrain, but not on uphill or downhill segments. The number of sites with 50% speed limit compliance increased from 4 to 12. The number of motor-vehicle crashes decreased from 10 to 9; the change was not significant, but injury crashes decreased from five to one. Regarding the residents, 30% were positive, 25% were negative, and 45% offered suggestions, some of which were conflicting. ::: ::: ::: DISCUSSION ::: Further study is needed on speed hump spacing and speed tables in hilly terrain. Example results should be shared with residents to inform their decision-making. ::: ::: ::: SUMMARY ::: At least 78% of the sites experienced a decrease in the mean or 85th percentile speed, or an increase in speed limit compliance. ::: ::: ::: IMPACT ON INDUSTRY ::: These findings should be useful to agencies that are planning or implementing traffic calming projects, and to analysts. <s> BIB003 </s> A THEORETICAL OVERVIEW OF ROAD HUMP EFFECTS ON TRAFFIC SPEED IN RESIDENTIAL ENVIRONMENTS <s> Related Literature on Effects of Road Hump Design <s> In the inhabited zones where a large number of pedestrians and other vulnerable road users are expected, like school zones, it is necessary to decrease the speed to such a level that the risk of vulnerability is the lowest possible. One of the commonly accepted and often implemented speed decrease measures is vertical raising of the road pavement (speed bumps, speed humps, etc.). This work shows the influence of speed bumps of different heights (3, 5 and 7 cm) to the decrease of vehicle speed. Speed measurements had been done before speed bumps were installed, 1 day and 1 month after the installation. Applying ANOVA analysis and post hoc analysis, using Tukey-Kramer's multiple comparison test, a comparison was made of mean, 50th percentile and 85th percentile speed, before and after speed bumps setting. It has been shown that there is a significant speed decrease on the places where speed bumps were set, compared to the period before setting. Based on the research results, it was suggested that on the locations where vulnerable road users are extremely endangered, speed bumps 5 and 7 cm high should be set, whereas at less endangered locations speed bumps 3 cm high could be set. Also, it has been shown that the effects of speed bumps on speed decrease are enduring, because there has not been any significant deviation in vehicle speeds neither 1 day nor 1 month after speed bumps setting. <s> BIB004 </s> A THEORETICAL OVERVIEW OF ROAD HUMP EFFECTS ON TRAFFIC SPEED IN RESIDENTIAL ENVIRONMENTS <s> Related Literature on Effects of Road Hump Design <s> In its most simple terms, traffic calming is about preserving the functions of local streets. As local streets are intended to provide primarily land-access services, hence, when traffic begins to use local streets for through movements, traffic volume and speed levels become incompatible with this primary function. To respond, a study on the effectiveness of traffic calming measures in reducing vehicles speed at Taman Setapak residential area was undertaken. Field observations and spot speed survey were conducted to collect primary data. The field observation was carried out to collect data on road geometrics and design characteristics of the road humps. The spot speed survey was administered to collect vehicles speed at different points near the road humps. The major findings include first, the road humps proved effective in reducing the speed of the vehicles and second the design characteristics of the road humps is an important factor in reducing the speed of the vehicles. The average speed of the vehicles before approaching the road humps was about 30 km/hr and at the road humps below 10 km/hr. The findings showed that the design profiles of the road humps have an impact on the speed of the vehicles; the gentle the design profiles of the road humps especially in terms of its height and slope, the higher the speed of the vehicles near and at the road hump. The findings also showed a clear difference in the average speed of the motorcars approaching the road hump and at the road hump. <s> BIB005 </s> A THEORETICAL OVERVIEW OF ROAD HUMP EFFECTS ON TRAFFIC SPEED IN RESIDENTIAL ENVIRONMENTS <s> Related Literature on Effects of Road Hump Design <s> Speed humps are designed to ensure the safety of both drivers and pedestrians. The use of speed humps on residential streets is an efficient way of controlling the speed of vehicles traveling on them. Based on observations made in a case study, different geometric combinations of speed humps are currently in use. Although there are a few guidelines that stipulate specific ranges of dimensions for the installation of speed humps, no perfect or ideal guidelines have been introduced and properly enforced by the local authorities. Therefore, because there are so many styles and inconsistent designs of the speed humps, a well-established empirical study has been implemented to develop the optimal designs of consistency models. In this study, the 85th-percentile speed reduction and discomfort level were related to the geometric design of the speed hump. The speed data were obtained by using a laser gun meter detector to attain the spot speed data at the selected speed hump location, while the vibration data collection were obtained using the triaxial acceleration transducers connected to Racelogic VBOX II SX. Multiple linear regression analyses were conducted to develop a statistical relationship between the variables. Two models were successfully developed and validated according to the statistical procedures in the study. These models can be used as a basis for the design of speed hump geometry for a selected 85th-percentile speed reduction and discomfort level. <s> BIB006
The importance of the hump design in controlling traffic speed was mentioned by  and BIB004 , who indicated that with an increase in the hump profile's height or severity, the post-entry speeds and speed in between a series of bumps will decrease. BIB004 evaluated the effectiveness of humps 30 mm, 50 mm and 70 mm height in inverse proportion to the traffic volumes along 3 selected roads, and noted that the speeds reduced with an increase in height. Given that this study made use of humps with similar depths, this means that the slope changes with an increase in height and is thus capable of affecting vehicle speeds. Another notable point made was that despite the significant speed reduction for a hump height of 30 mm, the speeds recorded would result in an 80% fatality rate in case of a vehicle-pedestrian collision. Hence this is fairly consistent with general literatures that recommend heights of 50-100 mm BIB001 BIB002 Malaysian Ministry of Road Works, 2012) . In addition, the study by BIB005 noted that the speed variations were larger in a hump of 60 mm height as compared to another hump of 80 mm height. The gentler slope of the 60 mm hump resulted in more vehicles exceeding the speed limit 30 m before and after the road hump. BIB006 also found that the hump height was positively correlated with the speed reduction between two measured points, and was also a statistically significant predictor in comparison to hump length and width. This study also developed a regression model to calculate the 85th percentile speed reduction between two selected points, in which the hump height and length at each point were used as predictors. The predictors can also be rearranged to identify the suitable hump height and length to use in order to achieve the desired speed reduction. Conversely,  found that hump width was a significant factor in affecting device operating speeds at road humps. The model in the study suggested that a lower hump width to road width ratio would result in lower speeds. On a road with 12 m width, a 6 m wide hump was shown to result in a 10 percent reduction in speed as compared to a hump of 11 m width. The relation between ratio and reduction was evidenced further when  commented that the percentage in speed reduction dropped to 2 percent in the case of a 6 m wide hump constructed over a road with 8 m width, compared to a 7 m wide hump. This means that with a larger ratio between hump width and road width, the speed reductions increase. However, a concern with narrower hump widths is that drivers may drive their vehicles along the edges of the humps in order to avoid the humps as much as possible. This was one of the negative comments given by respondents in a survey conducted by BIB003 . On the other hand, the study conducted by  failed to successfully prove the relationship between the hump profile and the driver selection of entry speeds. Thus they stated that the hump height/length ratio was not a good explanatory variable in assessing a driver's speed selection, as there was a wide variation of entry speeds observed. Their conclusion was that driver behaviour is also an important predictor in explaining the speed selection, concurring with  statement that the driving style is a factor to be considered if changes are to be made in the surrounding environment.