2013 Session: 403

• Dynamic Modeling of VISSIM Critical Gap Parameter at Unsignalized Intersections
  Abstract: Critical gaps are essential parameters in the modeling of traffic operations at unsignalized intersections and roundabouts, and they are main determinants in the calculation of intersection capacities. In microscopic simulation tools, they are basic vehicle-related variables, and their values and variations among the population are user-defined. Errors or oversimplifications of these basic variables may yield unrealistic results in terms of total throughput, queue lengths, waiting times, etc.In this study we propose a method to calibrate the critical gap parameter in microscopic simulations based on individual travel time observations, and a simple formulation for the calculation of critical gap parameters that takes into account the increasing risk taken by drivers on the minor street with increasing volumes on the major road. This new formulation allows a better match between accepted gaps observed in reality and the actual traffic conditions. The new methodology and model formulation have been used for calibration and validation of the minimum gap parameter of the software program VISSIM using data taken from several unsignalized intersections in the city of Leuven, Belgium. The results show clear outperformance of the volume-dependent model with respect to the conventional constant critical gap parameters.
  Authors: Viti, Francesco; Wolput, Bart; Tampere, Chris; Vandervelden, Pieter
  Authors: Viti, Francesco; Wolput, Bart; Tampere, Chris; Vandervelden, Pieter
  Year: 2013
  Document Type: Paper
  Subject: Operations and Traffic Management
  Session: 403
  Paper Number: 13-0597
• Complete Enough for Complete Streets? Testing the Sensitivity of HCM 2010 Multimodal Level of Service Under Conditions of Change
  Abstract: An increasing number of jurisdictions across the United States are exploring level of service (LOS) for multiple travel modes, in part due to the release of the 2010 Highway Capacity Manual (HCM 2010) as well as an increased focus on complete streets. One of the most important questions these jurisdictions are asking is whether new multimodal LOS (MMLOS) methods are sensitive enough to inform transportation investments, impact mitigation, or the prioritization of future projects. For this paper, transportation professionals (pubic, private, and academic) were surveyed about inputs they believed would have the greatest effect on pedestrian, bicycle, transit, and auto LOS or inputs they thought would have the greatest likelihood of being changed (i.e., to mitigate an impact or to improve existing conditions). Sensitivity testing was then performed at locations in four cities to measure how 2010 HCM MMLOS scores responded as these inputs were incrementally increased or decreased. While many inputs performed as expected, the testing also found cases where outputs were of a questionable direction or magnitude. The results of this study are informative for agencies considering adopting HCM 2010 MMLOS for purposes of mitigation, resource allocation, or strategic decision making. They also provide a starting point for additional research needed to enhance MMLOS methods.
  Authors: Carter, Peter; Núñez, Miguel; Peters, Sarah; Campbell, Julia; Martin, Francisco; Raykin, Leon; Milam, Ron
  Authors: Carter, Peter; Núñez, Miguel; Peters, Sarah; Campbell, Julia; Martin, Francisco; Raykin, Leon; Milam, Ron
  Year: 2013
  Document Type: Paper
  Subject: Operations and Traffic Management
  Session: 403
  Paper Number: 13-0786
• Pedestrian and Bicycle Level of Service at Intersections, Roundabouts, and Other Crossings
  Abstract: The Danish Road Directorate sponsored a study to develop methods for objectively quantifying pedestrian and cyclist stated satisfaction with roundabouts, signalized and non-signalized intersections, mid-block crossings, and pedestrian bridges and tunnels (in short: crossings). The results provide a measure of how well urban and rural crossings accommodate pedestrian and bicycle travel. In order to determine how existing traffic operations, geometric conditions, and other variables affect pedestrian and cyclist stated satisfaction, 180 randomly selected Danes were shown a total of 158 video clips from 95 crossings filmed by a walking pedestrian and a riding cyclist. Respondents rated crossings on a six-point scale ranging from very dissatisfied to very satisfied. This resulted in 3,023 pedestrian and 3,998 cyclist ratings. Crossings and video clips were described by about 300 variables.Pedestrian and cyclist satisfaction models were developed using cumulative logit regression of ratings and variables. The models include variables, which relate significantly (p <= 0.05) to the satisfaction ratings. Variables such as type, width and height of pedestrian and bicycle facility, length of crossing, size of roundabout, width of roadway, traffic volume, waiting time and speed limit significantly influence the level of satisfaction.Models return percentage splits of the six levels of satisfaction. These splits are then transformed into a level of service (LOS). The models provide traffic planners and others the capability to rate crossings with respect to pedestrian and cyclist satisfaction, and may be used in the processes of evaluating existing, designing new or redesigning existing crossings.
  Authors: Jensen, Søren Underlien
  Authors: Jensen, Søren Underlien
  Year: 2013
  Document Type: Paper
  Subject: Operations and Traffic Management
  Session: 403
  Paper Number: 13-0950
• Effect of Left Turns for Arterials with Queue Spillbacks
  Abstract: Traditional capacity calculation of signalized intersections does not take into account the effects of queue spillbacks that might occur at left-turn approach with two-lane section, i.e. an approach with one shared lane that expands to through movement and left turn lanes before the stop line at the intersection. As demand of the left-turn increases, and the storage capacity of the left-turn bay is limited, the probability of queue spillback occurrence increases. This is also correct for the through movements at its queue might also spillback to the shared-lane section. In this paper, we model the effects of queue spillbacks at the left-turn approach (both spillback from left-turn and through movements) on the capacity of the intersection, and as a result we also calculate the capacity drop. Afterwards, we extend our model to calculate the capacity of arterials with number of signalized intersections experiencing queue spillbacks at downstream approaches with two-lane section. Case study examples examine the effect of intersection characteristics (e.g. left-turn percentage, green durations, and storage capacity) on the arterial capacity drop. Finally, different left-turn control policies related to prohibit or permit left-turns at intersections are examined to increase the capacity of arterials. These control polices can help the traffic engineer practitioners not only to increase the capacity, but also to allocate efficiently the gained space from preventing left-turn to other transportation mode, e.g. bus lanes.
  Authors: Haddad, Jack; Geroliminis, Nikolas
  Authors: Haddad, Jack; Geroliminis, Nikolas
  Year: 2013
  Document Type: Paper
  Subject: Operations and Traffic Management
  Session: 403
  Paper Number: 13-1212
• Additional Lost Time due to Downstream Queue at Closely Spaced Intersections
  Abstract: At closely spaced signalized intersections, additional lost time can occur at upstream intersections when there is a queue spillback as a result of suboptimal signal timing. Closely spaced intersections are commonly seen at signal-controlled interchanges like diamond interchanges and partial cloverleaf interchanges. For a better estimation of capacities of closely spaced intersections, it is necessary to have an accurate model to calculate the additional lost time. The Chapter of Interchange Ramp Terminals in the Highway Capacity Manual 2010 provides a model for estimating additional lost time due to the presence of a downstream queue at closely spaced intersections. However, the HCM model does not provide a very accurate estimation when the distance to the downstream queue is short. In this paper, a new model is developed for an accurate estimation of additional lost time at closely spaced intersections, considering different factors that are not addressed in the HCM model or in previous research, like queue discharge pattern and traffic flow patterns. Simulation results indicate that the new model provides a more accurate estimation of additional lost time compared with HCM model in conditions when the distance to the downstream link is limited.
  Authors: Zhang, Zhen; Zong, Tian Z.
  Authors: Zhang, Zhen; Zong, Tian Z.
  Year: 2013
  Document Type: Paper
  Subject: Operations and Traffic Management
  Session: 403
  Paper Number: 13-1711
• Evaluation of the Functionally Hierarchical Road Network Considering Junction Types
  Abstract: A concept of the functionally hierarchical road network has been recognized since long ago, with the purpose of achieving higher network efficiency. In Japan, practical use of this concept is increasingly being demanded against the problems such as longer delay on arterial roads and larger flow of passing-through traffic on local roads. For that, the quantitative effects of typical measures of functional hierarchy, such as conversion of junction types need to be quantitatively demonstrated. Therefore, this study aims to evaluate the functionally hierarchical network considering the impact of junctions. The network is evaluated from two viewpoints: the performance of individual road levels and the performance of an entire network, by using several indices such as travel speed and use rate by through traffic on individual road levels. Since the existing methodologies cannot deal with the impacts of converting junction types on the travel speeds under the interaction with usersf route choice implicitly, an original UE assignment which takes into account junction delay by type is proposed. By applying it, a case study with hypothetical grid network showed that replacement of key signalized intersections between highest-level roads with overpasses is quite significant to form functional hierarchy and further improve the performance of the entire network. Additionally, it is also verified that junction treatment is more effective to improve mobility than enhancing of link free-flow speed under the network with dense signalized intersections.
  Authors: Goto, Azusa; Nakamura, Hideki; Asano, Miho
  Authors: Goto, Azusa; Nakamura, Hideki; Asano, Miho
  Year: 2013
  Document Type: Paper
  Subject: Operations and Traffic Management
  Session: 403
  Paper Number: 13-2535
• Travel Time Estimation for Signalized Arterials Using Probabilistic Modeling
  Abstract: Travel time is an important performance measure for transportation facilities. The objective of this research is to develop a model for estimating travel time for signalized arterials using probabilistic modeling. The model provides travel time based on the cycle length, green times, link lengths, maximum operating speed, offsets, acceleration/deceleration rate, and the per lane entering flow rate at each intersection. Results from the model were compared to a field data-calibrated simulator, and it was concluded that travel times from the simulation and the analytical model are similar and have similar trends. Increases in the g/C ratio and the acceleration/deceleration rate result in decreasing travel time. The impacts of other factors, such as link length, speed, and flow rate are not consistent: they mostly depend on the prevailing offsets. It was concluded that the analytical model can estimate the arterial travel time and its variability with reasonable accuracy.
  Authors: Li, Zhuofei; Elefteriadou, Lily
  Authors: Li, Zhuofei; Elefteriadou, Lily
  Year: 2013
  Document Type: Paper
  Subject: Operations and Traffic Management
  Session: 403
  Paper Number: 13-2614
• Multistage System for Planning Analysis and Signal Design of Diverging Diamond Interchange
  Abstract: As one of the most popular unconventional interchange designs, diverging diamond intersection (DDI) has received increasing attention over the past decade. This study, responding to the needs, has produced a reliable and convenient system for traffic engineers to perform operational analysis of DDI. The entire system comprises three modules for planning analysis, signal optimization, and operational evaluation. At the planning stage, this system presents a set of empirical equations for engineers to compute the overall interchange delay and identify the potential queue spillback locations in a DDI design. The second module aims to provide the optimal signal plans to prevent the potential queue blockage. This module is unique in its consideration of the interdependent relations between queues at a DDI¡¯s closely-spaced intersections, and the impacts by both geometrical constraints and traffic volumes. Given the traffic volumes, geometrical features, and signal timings, the system¡¯s third module provides users to link a VISSIM-based simulation model to estimate the resulting traffic queues and interchange delays. Numerical analysis with four real-world DDI designs has revealed the effectiveness of the proposed system.
  Authors: Yang, Xianfeng; Chang, Gang-Len; Rahwanji, Saed
  Authors: Yang, Xianfeng; Chang, Gang-Len; Rahwanji, Saed
  Year: 2013
  Document Type: Paper
  Subject: Operations and Traffic Management
  Session: 403
  Paper Number: 13-3245
• Volume-to-Capacity Estimation of Signalized Road Networks for Metropolitan Transportation Planning
  Abstract: Transportation planning has been playing a critical role in shaping economic health and quality of life. It not only provides insight into the mobility of people and goods, but also influences patterns of growth and economic activity. Metropolitan transportation planning is a challenging transportation topic because of the lack of future traffic information, like evaluating the capacity sufficiency on a large metropolitan road network with signalized intersections. The Highway Capacity Manual provides methods for analysis of signalized intersections and urban streets for planning. However, these methods need detailed traffic volume inputs and lane configurations at signalized intersections, which are normally not readily available in metropolitan transportation planning. The conventional four-step planning process is widely used to forecast directional traffic volumes on each road segment, but the projected volumes are not enough for analyzing capacity sufficiency of future road networks by existing methods. In this study, a simplified v/c ratio estimation procedure was developed based on available planning data and characteristics of signalized intersections. It links traffic assignment results of the conventional transportation planning procedure and capacity sufficiency estimation. By using the proposed method, transportation planners can estimate capacity sufficiency of future metropolitan road networks with available data in transportation planning. It will dramatically decrease the effort required for capacity evaluation of large metropolitan road networks.
  Authors: Xu, Hao; Liu, Hongchao; Fernando, Hiron; Senadheera, Sanjaya P.
  Authors: Xu, Hao; Liu, Hongchao; Fernando, Hiron; Senadheera, Sanjaya P.
  Year: 2013
  Document Type: Paper
  Subject: Operations and Traffic Management
  Session: 403
  Paper Number: 13-3410
• Effect of Access Point on Signalized Intersection Capacity
  Abstract: In the HCM2010, various factors were provided to adjust the base saturation flow rate for the capacity analysis of signalized intersections. There were, however, no factors to account for the potential change of signalized intersections capacity caused by the access point that located close to the signalized intersection. This paper presented a theoretical model for estimating the lane group capacity at signalized intersections with the consideration of the effects of access points. Two scenarios of access point locations, upstream or downstream of the signalized intersection, and impacts of six types of access traffic flow are taken into account. Results of extensive numerical analysis showed that the access point may have a substantial impact on the capacity, which has an inverse correlation with the number of major street lanes and the distance between the intersection and access point. And in the six types of access traffic flows, the access traffic flow 1 (right-turning traffic from major street), 4 (left-turning traffic from access point) and 5 (left-turning traffic from major street) would cause a more significant effect on lane group capacity.
  Authors: Zhao, Jing; Ma, Wanjing; Yang, Xiaoguang
  Authors: Zhao, Jing; Ma, Wanjing; Yang, Xiaoguang
  Year: 2013
  Document Type: Paper
  Subject: Operations and Traffic Management
  Session: 403
  Paper Number: 13-3277
• Capacity and Signal Timing Analysis of Signalized Intersections with Increasing Saturation Flow Rate
  Abstract: The traditional model of traffic flow at a signalized intersection explicitly assumes that the queue formed during the red time dissipates at a constant headway. Consequently, capacity is determined assuming that when a signal changes to green, the flow across the stop line increases rapidly to a constant discharge rate. This assumption has been challenged by some recent field observations conduced in Taiwan and USA, which showed marginal increase in queue discharge flow rate as the average headway decreases along the position of queued vehicles towards the back of queue. This paper investigates queue discharge behavior at signalized intersections based on data collected from six signalized intersections in Auckland, New Zealand. These field observations confirm what was observed elsewhere that the saturation flow rate increases with green time. An empirical model is proposed to incorporate this increasing trend in saturation flow rate for capacity and signal timing analysis. A methodology is devised based on Highway Capacity Manual to incorporate the proposed model, which showed prospect to handle the shortcomings of traditional model for practical applications in real world situations.
  Authors: Chaudhry, Mohsin Shahzad; Ranjitkar, Prakash
  Authors: Chaudhry, Mohsin Shahzad; Ranjitkar, Prakash
  Year: 2013
  Document Type: Paper
  Subject: Operations and Traffic Management
  Session: 403
  Paper Number: 13-3396
• Quantifying Measurement Error in Arterial Travel Times Measured by Bluetooth Detectors
  Abstract: Travel time is viewed by both travellers and road managers as one of the key qualities of service indicators. However, a relatively limited number of technologies are available that can measure travel times. Bluetooth detectors have recently emerged as a viable technology for acquiring vehicle travel times. A number of studies have been published describing the technology and comparing the measured travel times to travel times obtained via another technology. However, most of these studies have focussed on the application of Bluetooth detectors to freeway environments for which measurement errors tend not to be significant. In this paper we examine the application of Bluetooth detectors to acquire arterial travel times. The arterial environment is substantially more challenging as a result of the frequent interruptions in the traffic flow caused by the operation of traffic signals.In this paper we examine the magnitude of detection time and travel time measurement errors. It is not feasible to use field data to examine the measurement error because the error is inherent within the observations and cannot be separated. Consequently, we propose an evaluation framework that combines micro traffic simulation with Monte Carlo simulation to synthesize measurement errors for a range of arterial traffic condition. The results show that the mean travel time error is essentially zero for all traffic conditions. However, the variance of the error varies is a function of the traffic conditions. We develop a multivariate regression model to quantify the standard deviation of the travel time measurement error as a function of the traffic factors, and, using this model show that under some conditions, the 95% confident interval of the travel time measurement error may reach 25% of the true mean travel time. These results can be used to assess potential Bluetooth detector deployment plans and provide insight into the upper bound on the reliability of arterial travel time measurements obtained from Bluetooth detectors.
  Authors: Salek Moghaddam, Soroush; Hellinga, Bruce
  Authors: Salek Moghaddam, Soroush; Hellinga, Bruce
  Year: 2013
  Document Type: Paper
  Subject: Operations and Traffic Management
  Session: 403
  Paper Number: 13-4915
• Toward a Capacity Analysis Procedure for Nonstandard TWSC Intersections
  Abstract: Two-way stop-controlled (TWSC) intersections are one of the most common forms of at-grade roadway junctions in the world. These intersections typically reside where a minor road intersects or joins a major roadway with stops signs placed at the minor approach. When the major roadway, and the traffic it carries, goes straight through the intersection, it is a standard TWSC intersection.In many places, however, the prevailing traffic and the major roadway themselves do not continue straight through the intersection. In such cases the major roadway bends at an angle at the intersection and the stop signs on the minor streets subsequently are placed on adjacent legs of the intersections. These intersections are non-standard TWSC intersections. Non-standard TWSC intersections are found frequently in some and exist in most countries. They are officially recognized in traffic codes and manuals in Europe, Australia, and the United States, yet Highway Capacity Manual (HCM) TWSC procedure does not specifically handle these intersections. In fact, a literature review yielded no established procedure for calculating the capacity at non-standard TWSC intersections that would consider the specificities related to the layout of the approaching roadways and characteristics of traffic flow parameters, such as critical headway and follow-up headway.This paper demonstrates the uniqueness of non-standard TWSC intersections, reports analysis results from field data collected at several similar non-standard TWSC T-intersections, presents the large discrepancy in terms of critical headway figures and level of service based on HCM procedure for TWSC intersections, and calls for further research on the subject in other locales.
  Authors: Bogdanovic, Vuk; Ruskic, Nenad; Kulovic, Mirsad; Han, Lee D.
  Authors: Bogdanovic, Vuk; Ruskic, Nenad; Kulovic, Mirsad; Han, Lee D.
  Year: 2013
  Document Type: Paper
  Subject: Operations and Traffic Management
  Session: 403
  Paper Number: 13-5117
• Critical Lane Volume (CLV)-based Capacity and Level of Service Analyses for Diverging Diamond Interchange
  Abstract: Many traffic simulation software tools, such as Vissim, SimTraffic, Corsim, Synchro, and Dynasmart have emerged over the last decade and are widely used for analyzing capacity, delay, and level of service at intersections, ramps, and along arterial/freeway segments. While these tools have shown great promise, they are expensive and the data collection and input set-up is time consuming and resource intensive. Traffic engineers predominantly use one of those tools to analyze diverging diamond interchange (DDI), also known as double crossover diamond interchange. Developing a simulation model and performing required analysis takes considerable time and effort since it is not necessary to obtain detail traffic operational analysis of a DDI while interchange alternatives are being developed, a quick and easy evaluation procedure is warranted. In this paper, a critical lane volume (CLV) based analysis methodology is presented which could be an appropriate tool to bridge the gap. In this methodology, two intersection or nodes of a DDI, where through traffic movements along the arterial cross each other, are considered crucial. Understanding of the crossover movements, ramp movements, and coordination of traffic movements between the two nodes and lane configuration are used in developing the methodology. Critical movements are analyzed, compared and logically added to obtain the critical lane volume of the two nodes. The obtained critical lane volume is divided by intersection capacity to compute volume to capacity ratio and used in deriving the level of service of the two intersections in a DDI. The paper describes the mathematical formulation and analysis procedure to evaluate a DDI. Two real-world DDIs are analyzed using the developed method and compared with simulation results for reliability and accuracy.
  Authors: Maji, Avijit; Mishra, Sabyasachee; Jha, Manoj K.
  Authors: Maji, Avijit; Mishra, Sabyasachee; Jha, Manoj K.
  Year: 2013
  Document Type: Paper
  Subject: Operations and Traffic Management
  Session: 403
  Paper Number: 13-5118
• Capacity Reduction of Urban Roads due to Bus Stops
  Abstract:

  Road side frictions like buses stopping at bus stops, parked vehicles, pedestrian traffic, frequent side roads etc; which impede the smooth flow of traffic are unique features found along urban roads in developing countries. These road side frictions along with mixed traffic prevalent in developing countries have a detrimental effect on capacity of urban roads as well as pose a serious threat to the safety of road users. Quantification of the impact of various types of side friction in mixed traffic is a challenging task to traffic engineers. Among the various side friction factors, curb lane bus stops/bus bays are inevitable features found along an urban corridor. The type of bus stop, number of buses stopping in the bus stop simultaneously, frequency of arrival of buses, bus dwell time etc are some of the important parameters affecting the capacity of road stretches near bus stops. This paper deals with the quantitative analysis of the impact of bus bays and curb side bus stops on traffic flow characteristics of urban roads. The extent to which these affect the traffic flow is quantified with respect to reduction in capacity of road stretches. Capacity of road stretches having bus bay is found to be reduced by 8.1 % due to maneuvering and dwelling of buses in the bay, while for stretches having curb side bus stops the reduction is 25.6 %. Models are developed relating road capacity with bus dwell time for bus bays as well as for curb side bus stops.

  Authors: Rajamma, Ashalatha; Sasikumar, Salini; Prakash, Neethu
  Authors: Rajamma, Ashalatha; Sasikumar, Salini; Prakash, Neethu
  Year: 2013
  Document Type: Paper
  Subject: Operations and Traffic Management
  Session: 403
  Paper Number: 13-0070
• Additional Lost Time due to Downstream Queue at Closely Spaced Intersections
  Authors: Zhang, Zhen
  Authors: Zhang, Zhen
  Year: 2013
  Document Type: Presentation; Poster
  Subject: Operations and Traffic Management
  Session: 403
  Paper Number: 13-1711
• Revised Version of HCM 2010 Urban Streets Automobile LOS Methodology
  Authors: Ozkul, Seckin
  Authors: Ozkul, Seckin
  Year: 2013
  Document Type: Presentation; Poster
  Subject: Operations and Traffic Management
  Session: 403
  Paper Number: 13-2109
• Evaluation of the Functionally Hierarchical Road Network Considering Junction Types
  Authors: Goto, Azusa
  Keywords: poster presentation; poster design; poster template
  Authors: Goto, Azusa
  Year: 2013
  Document Type: Presentation; Poster
  Subject: Operations and Traffic Management
  Session: 403
  Paper Number: 13-2535
• Multistage System for Planning Analysis and Signal Design of Diverging Diamond Interchange
  Authors: Yang, Xianfeng
  Authors: Yang, Xianfeng
  Year: 2013
  Document Type: Presentation; Poster
  Subject: Operations and Traffic Management
  Session: 403
  Paper Number: 13-3245
• Volume-to-Capacity Estimation of Signalized Road Networks for Metropolitan Transportation Planning
  Authors: Xu, Hao
  Authors: Xu, Hao
  Year: 2013
  Document Type: Presentation; Poster
  Subject: Operations and Traffic Management
  Session: 403
  Paper Number: 13-3410
• Quantifying Measurement Error in Arterial Travel Times Measured by Bluetooth Detectors
  Authors: Salek Moghaddam, Soroush
  Authors: Salek Moghaddam, Soroush
  Year: 2013
  Document Type: Presentation; Poster
  Subject: Operations and Traffic Management
  Session: 403
  Paper Number: 13-4915
• Pedestrian and Bicycle Level of Service at Intersections, Roundabouts, and Other Crossings
  Authors: Jensen, Søren
  Authors: Jensen, Søren
  Year: 2013
  Document Type: Presentation; Poster
  Subject: Operations and Traffic Management
  Session: 403
  Paper Number: 13-0950
• Capacity and Signal Timing Analysis of Signalized Intersections with Increasing Saturation Flow Rate
  Authors: Ranjitkar, Prakash
  Authors: Ranjitkar, Prakash
  Year: 2013
  Document Type: Presentation; Poster
  Subject: Operations and Traffic Management
  Session: 403
  Paper Number: 13-3396
• Revised Version of HCM 2010 Urban Streets Automobile LOS Methodology
  Abstract:

  The Highway Capacity Manual (HCM) 2010 contains a significantly revised automobile analysis and level of service (LOS) methodology for arterials. This paper compared the arterial LOS results of the HCM 2000 and 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, as well as data received from FDOT Districts 2 and 3.The HCM 2010 results showed that for shorter/lower speed arterial segments (such as in central business districts) it was not possible to obtain LOS A or B. Thus, many of the 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 different revisions of the HCM 2010 methodology to find an approach that would not be as punitive to arterials with shorter segment lengths and 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 consist of the following: using two-classes instead of one (based on posted speed), using average travel speed as the service measure instead of the ratio of average travel speed to base free-flow speed, and setting free-flow speed equal to the posted speed plus five miles per hour instead of the free-flow speed computations in the HCM 2010 methodology.

  Authors: Ozkul, Seckin; Washburn, Scott S.; McLeod, Douglas S.
  Authors: Ozkul, Seckin; Washburn, Scott S.; McLeod, Douglas S.
  Year: 2013
  Document Type: Paper
  Subject: Operations and Traffic Management
  Session: 403
  Paper Number: 13-2109