Road-Traffic Studies Part One
TRANSPORTAION ENGINEERING SESSIONAL II
Traffic Volume Survey
List of Content
2. Scope and Objectives
4. Data collection
5. Data analysis
Traffic engineers and planners need information about traffic. They need information to design and manage road and traffic system. They use the information for planning and designing traffic facilities, selecting geometric standards, economic analysis and determination of priorities. They use this to justify warrant of traffic control devices such as signs, traffic signals, pavement markings, school and pedestrian crossings. The also use this information to study the effectiveness of introduced schemes, diagnosing given situations and finding appropriate solutions, forecasting the effects of projected strategies, calibrating and validating traffic models.
Transportation system is a dynamic system. Information about traffic must be regularly updated to keep pace with ever-changing transportation system. Data must be collected and analyzed systematically to get representative information. Traffic surveys are the means of obtaining information about traffic. This is a systematic way of collecting data to be used for various traffic engineering purposes.
1.1.a. Main purposes of traffic survey:
The main purposes of traffic survey are: traffic monitoring, traffic control and management, traffic enforcement, traffic forecasting, model calibration and validating etc.
1.1.b. Parts of traffic studies:
Traffic studies include:
Inventory of road traffic physical features
Traffic stream characteristics- volume, speed, density, occupancy studies etc. Capacity studies of streets and intersections
System usage studies- Travel time and delay, O-D survey Travel demand- home interview survey
Road users cost- Value of travel time, vehicle operating cost Parking supply & demand studies
Axle load survey
Mass transit performance and usage studies
Traffic accidents studies
Environmental impact studies of transport
1.2.Traffic Volume Study:
Traffic data are needed in research, planning, designing and regulation phases of traffic engineering and are also used in established priorities and schedules of traffic improvements. The traffic engineer must acquire general knowledge of traffic volume characteristics in order to measure and understand the magnitude, composition, and time and route distribution of volume for each area under his jurisdiction.
1.3.a. Volume/flow: The total number of vehicles that pass over a given point or section of a lane or roadway during a given time interval. It is the actual number of vehicle observed or predicted to passing a point during a given interval. 1.3.b. Rate of flow: The equivalent hourly rate at which vehicles pass over a given point or section of a lane or roadway during a time interval less than 1hr. usually 15 min. 1.3.c. Average Daily Traffic (ADT): The volume during a given time period divided by the number of days in that time period and expressed in terms of vpd. 1.3.d. Average Annual Daily Traffic (AADT): It is the total yearly volume divided by the number of days in a year and expressed in terms of vpd.
Scope and Objectives
2.1.Scope Of Traffic Volume Studies:
The traffic volume count study is carried out to get following useful information: Magnitudes, classifications and the time and directional split of vehicular flows. Magnitude is represented by volume of traffic. Vehicles are classified into some predefined classes based on vehicle size and capacity. In a two-way road, vehicles moving towards two directions are counted separately to get the proportion. Time and directional split is useful to identify tidal flow. Proportions of vehicles...