00935375

Component

https://doi.org/10.3141/1804-08

http://scholar.google.com...iner&publication_year=2002

The ability of an automated license plate reading (ALPR) system to convert video images of license plates into computer records depends on many factors. Of these, two are readily controlled by the operator: the quality of the video images captured in the field and the internal settings of the ALPR used to transcribe these images. A third factor, the light conditions under which the license plate images are acquired, is less easily managed, especially when camcorders are used in the field under ambient light conditions. A set of experiments was conducted to test the effects of ambient light conditions, video camcorder adjustments, and internal ALPR settings on the percent of correct reads attained by a specific type of ALPR, one whose optical character recognition process is based on template matching. Images of rear license plates were collected under four ambient light conditions: overcast with no shadows, and full sunlight with the sun in front of the camcorder, behind the camcorder, and orthogonal to the line of sight. Three camcorder exposure settings were tested. Two of the settings made use of the camcorder's internal light meter, and the third relied solely on operator judgment. The license plates read ranged from 41% to 72%, depending most strongly on ambient light conditions. In all cases, careful adjustment of the ALPR led to significantly improved read rates over those obtained by using the manufacturer's recommended default settings. Exposure settings based on the operator's judgment worked best in all instances.

This paper appears in Transportation Research Record No. 1804, Transportation Data and Information Technology Research.

English

p. 56-61

2002

Transportation Research Record

0309077303

Figures (7) ; References (4) ; Tables (4)

Automatic license plate readers; Field studies; Judgment (Human characteristics); Motor skills; Operators (Persons); Video imaging detectors

Ambient light conditions; Camcorder settings

Highways; Planning and Forecasting; I72: Traffic and Transport Planning

TRIS, TRB, ATRI

Dec 10 2003 12:00AM

• CLEANING OF MATCHED LICENSE PLATE DATA
• COMPARISON OF DISTANCE ESTIMATES FOR COMMODITY FLOW SURVEY: GREAT CIRCLE DISTANCE VERSUS NETWORK-BASED DISTANCES
• COSTS AND BENEFITS OF USING INTELLIGENT TRANSPORTATION SYSTEMS AS AN ALTERNATIVE DATA SOURCE: CASE STUDY
• DECISION SUPPORT SYSTEM FOR ADVANCED TRAFFIC MANAGEMENT THROUGH DATA FUSION
• DESIGN CHARACTERISTICS OF NATIONAL TRAVEL SURVEYS: INTERNATIONAL COMPARISON FOR 10 COUNTRIES
• DEVELOPMENT OF AN XML-BASED SPECIFICATION FOR TRAFFIC MODEL DATA EXCHANGE
• DYNAMIC CAMERA CALIBRATION IN SUPPORT OF INTELLIGENT TRANSPORTATION SYSTEMS
• EFFECT OF FIELD SETUP ON ACCURACY OF TRAFFIC DATA COLLECTION USING MACHINE VISION TECHNOLOGY
• ENABLING AND MANAGING GREATER ACCESS TO TRANSPORT DATA THROUGH METADATA
• ESTIMATING TRAVEL TIME SUMMARY STATISTICS OF LARGER INTERVALS FROM SMALLER INTERVALS WITHOUT STORING INDIVIDUAL DATA
• INTEGRATED SIGN ORDERING SYSTEM THROUGH NETWORKING AND RULE BASE APPLICATIONS
• MEASURING VARIABILITY IN TRAFFIC CONDITIONS BY USING ARCHIVED TRAFFIC DATA
• MONTE CARLO SIMULATION IN SAMPLING TECHNIQUES OF TRAFFIC DATA COLLECTION
• OBJECT-ORIENTED GEOGRAPHIC INFORMATION SYSTEM DATA MODEL FOR TRANSIT TRIP-PLANNING SYSTEMS
• PROTOTYPE CLASSIFICATION TOOL FOR SUPPORTING MAINTENANCE OF TRAFFIC SIGNAL TIMING PLANS
• REAL-TIME TRAFFIC MEASUREMENT FROM SINGLE LOOP INDUCTIVE SIGNATURES
• RECONSIDERATION OF SAMPLE SIZE REQUIREMENTS FOR FIELD TRAFFIC DATA COLLECTION WITH GLOBAL POSITIONING SYSTEM DEVICES
• REDUCTION OF VIDEO LICENSE PLATE DATA
• SIMULATION STUDY OF ESTIMATION OF INDIVIDUAL SPECIFIC VALUES OF TIME BY USING ADAPTIVE STATED-PREFERENCE SURVEY
• SPATIAL BEHAVIORAL DATA: COLLECTION AND USE IN ACTIVITY SCHEDULING MODELS
• TECHNIQUES FOR BUILDING MULTIJURISDICTIONAL GEOGRAPHIC INFORMATION SYSTEM PLATFORMS FOR TRANSPORTATION ANALYSIS
• TEMPORAL DATA CONSTRUCTS FOR MULTIDIMENSIONAL TRANSPORTATION GEOGRAPHIC INFORMATION SYSTEM APPLICATIONS
• TIME-USE METADATA
• TRANSIT VEHICLES AS TRAFFIC PROBE SENSORS
• TRAVEL-TIME ESTIMATES OBTAINED FROM INTELLIGENT TRANSPORTATION SYSTEMS AND INSTRUMENTED TEST VEHICLES: STATISTICAL COMPARISON
• USE OF INTERNET-BASED HOUSEHOLD TRAVEL DIARY SURVEY INSTRUMENT
• USE OF VESSEL FREIGHT DATA TO FORECAST HEAVY TRUCK MOVEMENTS AT SEAPORTS
• XML-BASED TRANSIT TIMETABLE SYSTEM