TRF - 2017
http://dl.lib.uom.lk/handle/123/17954
2024-03-28T09:36:39ZTransport Research Forum 2017 (Pre Text)
http://dl.lib.uom.lk/handle/123/20534
Transport Research Forum 2017 (Pre Text)
Pasindu, HR
2017-01-01T00:00:00ZGuideline to select appropriate locations for centre median openings
http://dl.lib.uom.lk/handle/123/18111
Guideline to select appropriate locations for centre median openings
Prasanga, HN; Pasindu, HR
Pasindu, HR
Medians are paved or landscaped areas in the middle of roadways that separate traffic travelling in opposite directions. A raised median with well-designed median openings is one of the most important tools to create a safe and efficient highway system. Moreover, it reflects the degree of access management of the particular highway.
At the moment, it can be clearly identified that many urban roadways in Sri Lanka are being rehabilitated and improved to multi-lane facilities with introducing raised road centre medians. Therefore, the provision of centre median openings for right turns, cross traffic movement & “U” turns is essential.
However, at the moment, there is lack of proper guidelines or a methodology available within road agencies in Sri Lanka to follow when deciding the appropriate locations for median openings of a particular highway. Most of the time frequent changes occur to the initial designs of the centre median and median opening locations due to the unavailability of a proper guideline. Often, there are lots of public requests for new median opening locations and it is very difficult to handle public requests in the absence of a proper guideline resulting delays to the centre median construction, deviating the objective of safety and proper access management. Therefore, this study is focused on developing a suitable guideline for the median opening selection process.
The proposed guideline has been developed based on some of the international access management guidelines and incorporating local considerations. Decision making criteria when justifying median opening locations is somewhat complex in nature since there is no proper legal framework available in Sri Lanka for access management.
Road network connectivity, road safety, traffic efficiency, right turning traffic volume density, the positioning of road side developments is some of the factors which influence the decision for selecting a proper location for median opening. The PTV VISSIM microscopic simulation model was used to optimize the selected median opening locations with respect to travel time and total delay of the road network. Vissim model has been used intensively around the world for such kind of access management experiments.
The median opening selection process is a complex process with regards to our country since we don’t have an access management policy. Therefore, it is very important to note that the median opening spacing are site specific and we cannot recommend a general spacing value for a road or a road section. If we go for general spacing values, that may be incorrect to use with the uneven positioning of by roads and different turning movement densities. Therefore, it is very difficult to provide a constant spacing for median openings in our road network. However, we can practice a minimum spacing value depend on functional requirements and safety.
2017-07-01T00:00:00ZEffects of road rehabilitation on road safety; analysis of accident trends
http://dl.lib.uom.lk/handle/123/18110
Effects of road rehabilitation on road safety; analysis of accident trends
Piyasena, MSKTDR; Bandara, JMSJ
Pasindu, HR
The purpose of rehabilitating the existing roads is to increase the level of service for the users. In that case increasing the level of safety of the road is a main concern. However, with the improvements, the resulting high-speed flow of vehicles and the safety issues in road designs cause changes in accident trends in newly rehabilitated roads. Analysing the accident trends helps to identify the contributory factors which cause the changes in accident trends and to eliminate those causes from future designs. Under this study, an analysis of road traffic crashes on selected rehabilitated roads in terms of descriptive statistics was carried out using ‘Sri Lanka Police Accident Database’ to find the road safety conditions of newly rehabilitated roads. Further with the purpose of an in-depth review of the causes of accidents a stepwise binary logistic regression was carried out on Padeniya - Puttalam road which has been newly rehabilitated in 2007-2009 as a case study.
2017-07-01T00:00:00ZAssessment of operating speeds of rehabilitated rural roads with asphalt surfacing
http://dl.lib.uom.lk/handle/123/18109
Assessment of operating speeds of rehabilitated rural roads with asphalt surfacing
Wijeratne, DDS; Mampearachchi, WK
Pasindu, HR
In Sri Lanka, rural roads are not specifically designed on technical requirements. Most of the rural roads (C and D classes) have historical backgrounds as being tracks and trails coming even beyond the colonial times. Hence, most of the rural roads in Sri Lanka are almost following the same traces and not designed technically. Nowadays, rural roads are being rehabilitated. So far, those rehabilitation projects underwent with merely construction improvements and proper geometrical improvements have not been adopted. It was found out that the actual speeds can be significantly greater after rehabilitation affecting the safety of road users. The aim of this study was to assess actual operating speeds, posted speed limits and to find design operating speeds that supposed to be after the rehabilitation. Finally, it suggests rational speed limits to rural rehabilitated roads under purview. Most of the rural roads in Sri Lanka haven’t posted speed limits specified according to the geometric, road environment and functionality level of the road. The speed limits of 70km/h and 50km/h are the usual speed limits enforced for traffic in arterial roads which are categorized as class A and B. Since the speed limits are not categorized according to the type of the road, above speed limits apply to the rural roads as well. It’s hardly been seen that traffic speeds are controlled or monitored by law enforcement on rural roads. Hence the speed choice of the rural road drivers depends on variety of other factors. The 85th percentile speed is taken as the operating speed. This speed has been used as a basis for suggesting rational speed limit since most drivers behave in a safe and reasonable manner and do not want to get into crashes. Also, it encourages drivers to travel at about the same speed. The researchers have studied a number of rehabilitated roads in North Western province in Sri Lanka. Each road is divided into several sections; straight and curved sections. Operating speeds on straight sections were given priority in suggesting rational speed limits. As operating speeds in curves are considerably lower and enforcing lower posted speeds only based on operating speeds on curves for entire road, would not be practical since drivers tend to disrespect the speed limit. The suggested rational speed limit for all the roads under purview is 50 km/h and this speed limit will be overridden to a lesser speed limit at a curved section based on the operating and design speed. This speed limit should be notified using sign boards and shall be enforced only for the curve itself.
2017-07-01T00:00:00Z