Evaluation of road humps on residential streets with different traffic characteristics

Abstract

An issue in regards to traffic calming in Malaysia is the lack of standardization in the guidelines and on-site implementation. Previous studies have noted the benefit of installing humps with higher dimensions, indicating that they result in higher speed reductions. However, such installations have resulted in concerns on increased noise levels, discomfort and difficulty in movement for the disabled. In addition, experiments involving 3D or illusion humps in Malaysia and overseas have found that the virtual illusion of humps can still result in speed reductions. The studies that note the benefit of higher humps are typically set at sites with similar geometric and functional characteristics, but many residential roads in Malaysian urban areas differ greatly in their characteristics. In addition, Malaysian hump guidelines are usually blanket guidelines with specific dimensions that do not take site differences into context. Thus a research gap that this study sought to fill is that it studies the effect of humps of varying dimensions on noise and vehicle speeds in different localities, which have different geometrical and functional characteristics. The research also sought to study the residents’ perception on the existing road humps in their residential areas and whether they have improved the living environment by reducing traffic noise, volume and vehicle speeds. The three areas selected for this research were Keramat, Setiawangsa, and Putrajaya, and in each area, two residential roads were selected to be assessed. The data were collected using traffic volume survey, inventory survey, speed and noise level surveys and a questionnaire survey that elicited responses from 478 respondents. The road humps were also evaluated based on criteria including land use, road and traffic characteristics in a scoring framework. A low hump height at areas with high traffic volume or high percentage of heavy vehicles was likely to result in minimal changes in noise levels, and residents disagreeing or feeling unsure with the humps’ effectiveness. However, it is concluded that the humps in this study largely did not result in noise level changes that were perceptible to the human ear. The perceptions were mostly influenced by the existing traffic noise, which was influenced by the traffic volume and composition. It was also found that in different localities, hump dimensions alone do not account for the evaluation of a hump’s effectiveness. The selected humps were effective in reducing vehicle speeds, but the humps of similar height/ width ratios at different areas resulted in statistically significantly different speed reductions due to the influence of the road gradient, traffic volume and proximity to intersections. 1980s/1990s residential developments or newer planned/ gated ones characterized by narrow to medium width roads, low to medium traffic volume and road gradients can still benefit from road humps of height/ width ratio of 0.017 to 0.018. The scoring framework also indicated that the proximity to a feature that affects traffic flow can also affect the effectiveness of different humps along the same road, even with both humps being in the same traffic calming segment and having similar dimensions. This research contributes by providing a method of evaluating road humps in different localities, and it can be used to improve the local authority guidelines for installing road humps based on the geometrical and functional characteristics of the areas.