Measures of Effectiveness for Level-of-Service Assessment of Two-Lane Roads: An Alternative Proposal Using a Threshold Speed (original) (raw)
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Evaluation of Performance Measures for Two-Lane Inter-urban Highways under Mixed Traffic Condition
The traffic performance of a highway is expressed in terms of level of service (LOS). It is a major input to important decisions on public fund investments that are made at different stages of the highway life. Because of its unique operational characteristics the evaluation of traffic performance on two-lane highways is not an easy task. The objectives of this research are (a) to examine the applicability of various performance measures for two-lane highways under mixed traffic conditions (b) to assign threshold values for different levels of service based on the best performance measure observed. Graphical and statistical analysis are carried out among the six most popular performance measures and traffic volume. No measure was found reliable for mixed traffic conditions. Therefore, the number of followers (NF) was introduced as a new performance measure. In mixed traffic conditions, followers are defined as vehicles travelling with gap less than 2.5s. Although NF is found to have good correlation with flow rate, it was also not able to reflect the true congestion conditions of a roadway. Therefore, this parameter is further modified to number of followers as a proportion of capacity (NFPC). It demonstrated a very strong correlation with traffic volume. Threshold values are proposed for different LOS based on NFPC for mixed traffic conditions.
Transportation Research Record, 2013
The Highway Capacity Manual 2010 (HCM 2010) contains a significantly revised automobile analysis and level-of-service (LOS) methodology for arterials. This study compared the arterial LOS results of the HCM 2000 and HCM 2010 methodologies for an experimental set of arterial segments and analyzed the effects of the revised methodology. In addition, existing Florida field data sets were also analyzed with arterial segments obtained from Gainesville, Tallahassee, and Tampa, all in Florida, as well as data received from the Florida Department of Transportation Districts 2 and 3. The HCM 2010 results showed that for shorter, lower-speed arterial segments [such as in central business districts (CBDs)] it was not possible to obtain LOS Ratings A or B. Therefore, many CBD arterials that had good LOS values under the HCM 2000 methodology would now have moderate to poor LOS values. Consequently, the research team tested several revisions of the HCM 2010 methodology to find an approach that would not be as punitive to arterials with shorter segment lengths and that would provide a good balance of LOS values across a range of segment lengths, posted speeds, and traffic demands. Suggested revisions to the HCM 2010 methodology that allowed this objective to be achieved consisted of the following: the use of two classes instead of one (on the basis of the posted speed); the use of the average travel speed as the service measure instead of the ratio of the average travel speed to the base free-flow speed; and the setting of the free-flow speed to equal the posted speed plus 5 mph, instead of using the free-flow speed computations in the HCM 2010 methodology.
Operational Performance Measures for Two-lane Roads: An Assessment of Methodological Alternatives
Procedia - Social and Behavioral Sciences, 2013
Two-lane roads represent the majority of the highway system in India. The analysis of traffic performance on two-lane roads is critical for their planning, design, maintenance, rehabilitation, and operation. It is a major input to important decisions on public fund investments that are made at different stages of the highway life. Performance evaluation is typically carried out with the capacity analysis for various highway facilities. Many countries in the world have a standard methodology for capacity analysis procedure. In general, performance of a highway is expressed in terms of level of service (LOS), which is a scheme intended to depict traffic conditions for an existing or proposed transportation facility operating under current or projected traffic demand. Evaluating the performance of the two-lane roads is not an easy task because of several distinct characteristics associated with these roads. IRC: 64-1990 provides some guidelines for capacity of two-lane roads; however, these guidelines provide very little information on LOS and its evaluation on these roads. As a result of that planners in India use the methodologies given in the Highway Capacity Manuals (HCM) of other developed countries. But these methodologies may not be applicable for Indian mixed traffic condition. This adoptation can cause serious consequences in situations where capacity augmentation by widening of the roads will cost huge amount of money. Therefore, it is necessary to examine the concerns expressed above and evaluate operational performance measure(s) used by researchers across the globe which would be appropriate and applicable to Indian conditions. This paper summarises the evolution of research on determining the LOS of two-lane roads and provides a discussion for future directions pertinent to Indian mixed traffic situation.
A mini review on percent time-spent-following (PTSF) as the service measure for two-lane highways
Communications in Science and Technology, 2018
Percent Time Spent Following (PTSF) is used by the Highway Capacity Manual (HCM) as one of the service measures to assess the level-of-service of two-lane highways since the 2000 edition. But, the problem facing to estimate this parameter is that the difficulty to measure it directly in the field. From several studies, it is known that the HCM analytical procedures applied in PTSF estimation produces inconsistent results with the 3 s surrogate measure and most of them are overestimate. This paper presents a review on estimating PTSF on two-lane highways from several studies that adopted HCM procedures.
Performance measures on two-lane highways: Survey of practice
Research in Transportation Economics, 2018
Two-lane highways constitute a significant component of the highway system and serve an essential function for the movement of people and goods. The Highway Capacity Manual is primarily used for operational analysis on two lane highways in the U.S., Canada and a few other countries outside North America. As part of a project sponsored by the National Cooperative Highway Research Program for improving the two-lane highway operational analysis methodology, a practice survey was conducted to gather information on agency experiences and preferences in regards to performance measurement on two-lane highways. The survey was sent to all state Departments of Transportation (DOTs) in the United States and Canada. A total of 35 usable responses were received, representing 25 states and 4Canadian provinces, with a few agencies sending multiple responses. This paper summarizes the results of the agency survey and presents the most important findings. Results suggest that the top three criteria for good performance measures on two-lane highways are: sensitivity to traffic conditions, sensitivity to road conditions, and relevance to road user perception. Further, agencies identified average travel speed as the most relevant traffic flow aspect to two-lane highway operations. Other performance measures that were found meritorious were volume-to-capacity ratio and flow rate, for class I and class II highways, respectively, versus average travel speed, volume-to-capacity ratio, and percent-time-spent-following for class III highways.
Measuring Level of Services on Multi-Lane Expressways by Platoon Parameters
Doboku Gakkai Ronbunshu, 2004
Platoon characteristics were introduced to measure service quality on multi-lane highway. The data used were collected from 18 locations on Tomei expressway. Due to the lack of study on platoon behavior on multi-lane highway, new platoon criteria and platoon behavior were investigated. Critical Headway was determined by relative speed method and exponential model. Platoon characteristics were explained by platoon rate, platoon size and percent of followers. New levels of service criteria, which based on road users points of view was proposed based on platoon parameters.
Assessing and Comparing Level of Service at National Highway
The Level of Service is a qualitative estimate relating operational conditions inside a traffic stream, and their perception by drivers or passengers. The present finding primarily aims at examining and comparing the level of services for national highways of a Nagpur (new metropolitan city) by using Highway Capacity Software (HCS-2000) and Highway Capacity Manual (HCM-2000). The study presented aims at national highway midblock sections for evaluation of the level of service. The field survey is carried out to express the traffic volume as well as the corresponding average spot speed of traffic through manual as well as videography technique. Since the examination is carried out at the mid-block sections rather than at the intersections the level of service F is not going to detect anywhere. The result gained by HCS-2000 method was compared to the result gained by HCM method. In noted conclusion Level of Service is a function of Speed and volume, the decrease in speed as a outcome of increase in traffic volume will lead to the fall of Level of Service. Comparison estimated of Flow and Density data of HCM with HCS are very close. The obtained LOS will be suitable in inspecting traffic quality based on the volume.
Measuring Performance on Two-Lane Highways: Empirical Investigation
Transportation Research Record: Journal of the Transportation Research Board, 2017
This paper presents an empirical investigation into several performance measures for operational analysis on two-lane highways. The performance measures investigated are average travel speed, average travel speed to free-flow speed, percent followers, followers flow, followers density, percent impeded, impeded flow, and impeded density. Field data from 16 study sites in the states of Montana, Idaho, Oregon, and North Carolina representing Class 1, Class 2, and Class 3 highways were used in this study. The level of association between performance measures and some of the most important traffic variables was examined with graphical and statistical techniques. The traffic variables investigated in this study included combined flow in both directions of travel; proportion of traffic in the direction of travel, called in this study “traffic split”; percentage of heavy vehicles; and speed variance. Study results suggest that speed-related measures have weak associations with traffic varia...
Traffic Performance Measures on Two-Way Two-Lane Rural Highways
Journal of Engineering Research and Reports
The most appropriate service measure for a two-lane highway is the combination of average travel speed (ATS) and percent time spent following (PTSF). The local driver behavior and traffic operation characteristics in different countries affect the operational analysis results. The objective of this study is to evaluate the applicability of the HCM procedures on two-lane highways in Iraq. Ten highway segments in northern Iraq were selected, and more than 28,000 vehicles were observed to record traffic characteristics. The results show that for low flow rates, the HCM-2000 procedures tend to overestimate the ATS with an amount of 0.0085VP, while for moderate-to-high flow rates, the HCM procedures tend to underestimate the ATS with an amount of 0.0025VP for the highways considered. Moreover, the HCM procedures tend to overestimate PTSF; as well, ATS decreases as PTSF, density, and follower density increase for the highways under study. Equations are developed for the evaluation of tra...