CE 341 Transportation Planning Data Management & Diagnosis

Transport Planning Database Foundation of effective Transportation Planning Objectives of Collecting data Determine existing conditions Calibration and application of travel forecast models Evaluation of overall performance of systems operation Gauging the degree to which planning goals and objectives are achieved Two major types: Quantifiable data used in technical analysis Subjective information (political/decision making process)

Traffic Study Data Traffic studies consist of 3 primary activities: Data Collection: Observing, gathering and recording data. Data Reduction: Coding, data entry, and tabulation. Data Analysis: Processing of data to understand the observed situation, diagnosis, and plan improvements.

Types of Traffic Data Traffic data could be grouped into 4 broad categories: Physical inventories: Street and highway inventories, control devices, parking spaces, roadway conditions. Population characteristics: Describe various aspects of road users, their vehicles, route, and travel behavior. Operational parameters: The measures that quantify the characteristics of traffic streams in motion: volume studies - Speed studies Travel time studies - Delay studies 4. Special Purpose data: Accident data - Parking studies Pedestrian studies - Goods movement &transit studies

Sampling Method in Data Collection It is infeasible - practically and economically- to develop a database consisting of every single element of Target population. Steps in planning and executing survey: Establish survey objectives Define target population Identify the specific relevant data to collect Specify the degree of precision required Determine method to be used in obtaining survey results Select the sampling procedures and sample size Pretest the survey Determine the procedure for analysis for analyzing and summarizing data

Types of Sampling Procedures Simple random sampling: Select units out of population such that each population unit has an equal chance of being drawn. Sequential sampling: Draw sample from every nth element in the population Stratified random sampling: divides the population of N units into sub-populations (N1, N2, …, NL) units, according to differences in some defining characteristics. Random samples are then taken within each strata. Cluster sampling: Grouping sampling units usually on a spatial or geographic basis. Clusters are then selected at random for sample

Determining Sample Size Accuracy of estimates increases with the size of the sample Degree of accuracy should be balanced against the cost of survey sampling Determination of sample size involves two major steps: Make assumption about the population distribution Make decision about the acceptable limits of error

The Normal Distribution Normal Distribution is defined by: The Mean: μ The Standard deviation: σ Probability of occurrence is measured by the surface area under curve.

Confidence Level Level of confidence (1-α): reflects the percentage of samples falling within the desired limit of error.

Sample Size n = [ z1-α . σ]² d Where: n = sample size d = tolerable margin of error of mean value σ = standard deviation of population distribution α = fraction of area under Normal curve representing event NOT within confidence level z1-α = Standard normal statistics corresponding to the (1- α) confidence level

Data Collection Survey Techniques Street Inventory Household Travel Behavior Automatic Traffic Count Manual Classification Count Turning Movement Count Speed Survey Origin-Destination Survey a- Roadside interviews b- Self-completion form c- Vehicle plate number

Street /Highway Inventory The inventory covers: street name, classification transit route & bus stops abutting land uses and driveways lighting curb parking conditions right-of-way utilization (lanes, sidewalk, pavement, medians) traffic flow directions traffic signs details traffic signal details traffic safety devices

Household Survey Very important in urban transportation planning Provide timely data on socioeconomic characteristics and travel behavior Three basic techniques: personal interviews: Best way of getting info. personal interaction, high response rate, time consuming, expensive telephone interviews mail survey

HH survey Data Some of HH Records address no of persons>5years genders total trips made motorized vs. non-motorized persons employed occupation income drivers status no. of cars Some Person Records Age, gender Occupation, industry, income Trip made Origins and destinations made Purpose “from” Purpose “to” Starting time of each trip Arrival time of every trip Mode of travel No. of persons in car Kind of parking Principal route of travel

Automatic Traffic Count ATC Mechanically measure volumes Some types: Pressure tube (hose) Magnetic (inductive) Radar Video image processing Temporary Permanent

Time Volume % 1:00 179 1.1% 2:00 121 0.8% 3:00 83 0.5% 4:00 61 0.4% 5:00 80 6:00 127 7:00 674 4.2% 8:00 1203 7.5% 9:00 1131 7.1% 10:00 1007 6.3% 11:00 1077 6.7% 12:00 1001 6.2% 13:00 988 14:00 925 5.8% 15:00 1069 16:00 1028 6.4% 17:00 989 18:00 920 5.7% 19:00 876 5.5% 20:00 765 4.8% 21:00 630 3.9% 22:00 492 3.1% 23:00 362 2.3% 24:00 251 1.6% Totals 16038 100.0% Hourly Flow: Traffic pattern Peak hour determination Average daily traffic ADT

Manual Classification Count MCC Carried out for short period of time Normally 15-mn interval Classify traffic into vehicle classes: cars, taxi, vans, pickup, truck, trailer, bus, etc. Counting techniques: Five-bar gate on paper Tally counter Hand-held electronic machines

Turning Movement Count TMC Manual count carried out with: Five-bar gate on paper Tally counter Hand-held electronic machines

Turning Movement Count TMC Carried out at junctions during peak periods 15-minute intervals Record directional volumes Sometimes classify the turning vehicles (especially left turns into light and heavy vehicles) Very important for junction operation analysis

Speed Survey Three types: Spot speed for individual vehicles using “radar gun”. Vehicle in the traffic flow traveling a certain distance using in-vehicle measuring equipment Speed of Journey

Time Vs. Space Mean Speed Time Mean Speed Is the average speed of vehicles passing a point over a specific time period. V=Σt Vt/n Where: V = time mean speed Vt = speed of individual vehicle n = number of vehicles observed Space Mean Speed Is the average speed of vehicles traveling over a measured distance. V=nL/Σi Ti Where: V = space mean speed ti = travel time of the ith vehicle n = number of vehicles observed

Origin-Destination Survey Ask drivers the origin and destination of their trips. Sample-based survey Selection of unbiased sample Define Traffic Analysis Zones TAZs, cordons, and screen lines

O-D Survey Techniques Roadside Interview: drivers are stopped at the side of the road Take safety measures during survey Self-Completion Forms: Usually performed via mail Easier, but sample may not be representative. License Plate Survey: Record portion (or all) license plate number and time at some stations Match license number to determine the origin, destination and path of the vehicle