Traffic Flow and Analysis of Roads Module 8 PDF

MODULE 8 TRAFFIC FLOW AND ANALYSIS OF ROADS  LEVEL OF SERVICE ANALYSIS Level of Service (LOS) analysis for highways is a critical part of transportation engineering used to assess the operational efficiency and quality of traffic flow. The procedure involves evaluating various perf...

MODULE 8 TRAFFIC FLOW AND ANALYSIS OF ROADS  LEVEL OF SERVICE ANALYSIS Level of Service (LOS) analysis for highways is a critical part of transportation engineering used to assess the operational efficiency and quality of traffic flow. The procedure involves evaluating various performance measures to categorize the service level experienced by drivers. Here are the detailed steps for conducting an LOS analysis for highways:  Step-by-Step Procedure 1. Define the Analysis Objectives and Scope  Objective: Identify the purpose of the analysis, such as traffic impact studies, roadway design, or improvement planning.  Scope: Specify the highway segment, intersection, or network area under analysis, including the study period (e.g., peak hour, average day).  Conditions: Determine analysis conditions (e.g., weekday vs. weekend, seasonal factors). 2. Data Collection  Traffic Volume Data: Collect data such as Average Annual Daily Traffic (AADT), Peak Hour Volume (PHV), and directional splits.  Speed and Travel Time Data: Measure speeds and travel times using radar, loop detectors, GPS devices, or travel time surveys.  Geometric Data: Collect data on the number of lanes, lane width, shoulder width, median type, and access points.  Environmental Conditions: Note factors such as weather conditions, work zones, and lighting.  Heavy Vehicles: Gather data on the percentage of heavy vehicles since they affect flow rates and capacity. 3. Classify the Highway Type  Uninterrupted Flow Facilities: Freeways, multilane highways without traffic signals.  Interrupted Flow Facilities: Urban streets, arterials, and highways with intersections or traffic signals. 4. Establish Base Condition  Determine base conditions representing ideal operational conditions: good weather, clear roadways, and free-flowing traffic.  Adjust base conditions based on lane widths, lateral clearances, grade, heavy vehicle presence, and driver population. 5. Calculate the Highway Capacity  Use the Highway Capacity Manual (HCM) methodologies to calculate capacity in terms of passenger cars per hour per lane (pcphpl).  Adjust capacity for factors like heavy vehicle percentages, terrain, and roadway design elements. 6. Determine Performance Measures  Flow Rate: Calculate flow rates by adjusting traffic volumes for observed conditions.  Density: Calculate density (vehicles per mile per lane) using the flow rate and speed data.  Speed: Measure average speed directly or estimate it using flow-density relationships.  Delay and Queue Length: Particularly for interrupted flow facilities, assess delay and queue length at critical points like intersections. 7. Determine the Level of Service (LOS) Using thresholds defined in the HCM, categorize the segment’s performance into one of six LOS levels (A through F), where:  LOS A: Free flow with high speeds and low traffic volumes.  LOS B: Stable flow with slight speed reductions.  LOS C: Stable flow with restricted maneuverability.  LOS D: High-density flow approaching capacity limits.  LOS E: At or near capacity with significant delays.  LOS F: Breakdown flow with frequent stop-and-go conditions. 8. Analysis and Interpretation  Compare the observed LOS with acceptable thresholds or target LOS.  Identify critical issues such as bottlenecks, excessive delays, or high density that reduce LOS. 9. Recommended Improvements  Based on LOS analysis, recommend potential improvements, such as lane additions, signal optimization, ramp metering, or access management.  Consider short-term operational fixes and long- term infrastructural changes. 10. Documentation and Reporting  Prepare a comprehensive report documenting the objectives, methodology, data sources, calculations, LOS results, and recommended improvements.  Use charts, tables, maps, and diagrams to visually present findings and support conclusions. Tools and Software  Highway Capacity Software (HCS)  Synchro/SimTraffic  VISSIM  AIMSUN  References Manual on Uniform Traffic Control Devices (MUTCD), 2009 Edition - Federal Highway Administration (FHWA). Highway Capacity Manual (HCM), Sixth Edition, 2016 - Transportation Research Board, Washington, D.C. Highway Capacity Software (HCS7) User’s Guide - McTrans Center, University of Florida. Transportation Research Board (TRB) Special Report 209 - Guidance on the Highway Capacity Manual updates.