Ttds.pdf

TRAVEL TIME AND DELAY SURVEY RECOMMENDED FORMAT FOR A SURVEY REPORT 1. Name of Survey 2. Purpose (Original intent as specified in the survey plan) 3. Description of the Study Area 4. Output (Most important findings) 5. Method/Procedure of Data Collection 6. Analysis (Discussion of results an...

TRAVEL TIME AND DELAY SURVEY RECOMMENDED FORMAT FOR A SURVEY REPORT 1. Name of Survey 2. Purpose (Original intent as specified in the survey plan) 3. Description of the Study Area 4. Output (Most important findings) 5. Method/Procedure of Data Collection 6. Analysis (Discussion of results and procedure followed to arrive at the conclusions) 7. Appendices TRAVEL TIME AND DELAY STUDIES Recording the time it takes vehicles to traverse a specified length of roadway Can determine the locations, types, and extent of traffic delays Purpose of Travel Time and Delay Studies To evaluate the quality of traffic movement Before and after” studies Determination of level of service Traffic assignment Economic studies Trend studies Definition 1. TRAVEL TIME STUDIES: Determines amount of time required to traverse a specific route or section of street or highway. The data provides travel time and travel information. 2. DELAY STUDIES: provides information on amount, location, duration, and frequency of delays and travel time. 3. TRAVEL TIME: Total elapsed time of travel (including stops and delays) over a specified route under existing traffic conditions. 4. RUNNING TIME: Portion of travel time that the vehicle is in actual motion = Travel Time - Stopped Time Delay Definition 5. TRAVEL SPEED - Overall average speed along a specified section of a street or highway = distance / travel time 6. RUNNING SPEED: Average speed along a specified route without stopped time. = distance / running time 7. DELAY - time lost by traffic due to traffic friction, traffic control devices and geometric design Definition 9. FIXED DELAY: Delay regardless of amount of traffic volume and interference present. Not a result of flow characteristics of traffic stream and could occur with only one (1) vehicle traveling in the section. E.g. Traffic signals, YIELD signs, STOP signs, Railroad crossings. 10. OPERATIONAL DELAY: Delay caused by interference from other components of traffic stream. E.g. Time consumed while waiting at the Stop sign for a gap in cross traffic Definition 11. TRAVEL-TIME DELAY: the difference between the actual time required to traverse a section and the time corresponding to average speed of traffic at a point of uncongested flow on the section. Includes acceleration and deceleration delay in addition to stopped time delay = (actual travel time) - (time corresponding to average speed of traffic at a point of uncongested flow) Definition 11. TRAVEL-TIME DELAY: the difference between the actual time required to traverse a section and the time corresponding to average speed of traffic at a point of uncongested flow on the section. Includes acceleration and deceleration delay in addition to stopped time delay = (actual travel time) - (time corresponding to average speed of traffic at a point of uncongested flow) TTD STUDIES - METHOD Test Car Technique Floating Car Technique Average Speed Technique Maximum-car Technique Video License Plate Technique or Number Plate Survey Interview Technique TEST CAR TECHNIQUE Materials/Equipment Voice Recorder Stopwatch Laptop Form & Pencil/Pen Tablet / Ipad Vehicle GPS Video Camera Manpower Action Camera Driver Smartphone App Observer(s)/recorder TEST CAR TECHNIQUE A test vehicle is driven over a “test” section or study route in a series of runs. The time readings as the vehicle passes each station are recorder. When the vehicle stops or is forced to travel slowly, the time, location and cause are recorded on the field sheet. TEST CAR TECHNIQUE “FLOATING CAR” TECHNIQUE - the driver attempts to approximate the median speed by passing as many vehicles as pass his/her vehicle “AVERAGE SPEED” TECHNIQUE - test vehicle travels at a speed that the driver believes to be the speed representative of the speed of all traffic at the time “MAXIMUM-CAR” TECHNIQUE - test vehicle is driven at the posted speed limit unless impeded by actual traffic conditions or safety considerations. Sample Size Requirements with Confidence Level of 95.0% Average range in = Sum of calculated speed differences running speed Number of completed test runs - 1 Procedure 1. Define the study area by selecting all control points before beginning the study. Control points are nodes at the beginning or end of a link, usually the stop line at a signalized intersection, but can be any physical feature, i.e., power pole 2. Conduct during average or typical weekday traffic conditions during reasonably good weather so that unusual conditions do not influence the study. The time periods recommended for studies are A.M. and P.M. peak hours as well as off peak hours in the direction of heaviest traffic movements. 3. Estimate the number of runs; Make additional runs if required. 4. Select what technique to use. License Plate Technique when only travel time information is desired, the average travel speed can be calculated. Observers are stationed at the entrance and at the exit of the test section. The vehicle plate number of vehicles that pass the observer is then recorded along with the time. The numbers are then matched in the office, either manually or by computer. Travel Time = Exit Time - Entrance Time sample size of 50 license number matches usually provides adequate accuracy (Box and Oppenlander 1976). Other variations: use of sticker or card sticked/given at the entrance and taken at the exit. Video Survey use of video camera. Can observe other activities like the turning movements, parking and loading. Can be viewed repeatedly. Important is the location of the camera, there might be obstructions from the vehicles near the camera. Interview Technique To obtain needed information from the transportation users themselves. Also from transportation service providers and policy makers. The primary data concern the recent trip-making patterns and certain indicators that describe the individua’s social, economic and mobility status Large amount of materials in a minimum of time and at little expense. e.g. Employees at strategically located firms are asked to log their travel time to and from work on one particular day Presentation of Results 1. Time vs distance diagram 2. Speed vs distance diagrams can be graphed. 3. Time contour maps or Isochronal charts also provide a graphical representation of the quality of traffic flow. The contour lines or isochrons represent time (minutes) of travel time from central reference point. Time contour maps are particularly well-suited for comparison of the various routes leading from the central business district (CBD) and for estimating the time that may be saved by planning a new or improved facility. Time-Distance Diagram Speed-Distance Diagram Travel time contour map Travel time contour map