An Investigation of the An Investigation of the Distribution of Driving Distribution of Driving Speeds Using InSpeeds Using In--vehicle vehicle GPS Data GPS Data

Jianhe DuJianhe DuLisa AultmanLisa Aultman--HallHall

University of ConnecticutUniversity of Connecticut

Problem StatementProblem Statement

Traditional speed collection methods Traditional speed collection methods can not record drivercan not record driver’’s individual s individual informationinformationDoes speed vary by age or sex?Does speed vary by age or sex?Do certain roads consistently have Do certain roads consistently have larger average speed to speed limit larger average speed to speed limit ratio?ratio?

Our Research GoalsOur Research Goals

Collect GPS data that can be linked to Collect GPS data that can be linked to driversdrivers’’ demographic informationdemographic informationCompare the speed profile of men Compare the speed profile of men versus women and among different versus women and among different age groupsage groupsCompare the ratio of average speed to Compare the ratio of average speed to speed limits on different road typesspeed limits on different road types

OutlineOutline

InIn--vehicle GPS data collectionvehicle GPS data collectionData processingData processingAnalysis of speed distributionsAnalysis of speed distributionsConclusionsConclusions

GPS Device Used in the StudyGPS Device Used in the Study

TRIMBLE II GPSTRIMBLE II GPS

Attributes of the Attributes of the GarminGarminInstrumentInstrument

GPS receiver performance– Tracks up to 12 satellites– Update rate: 1 second– Position Accuracy - Non-differential GPS: 15 meters RMS– Velocity Accuracy - 0.2 m/s RMS steady state

Logging options– Record position only, position and speed only, or position,

speed, and altitude– Record at either 1-second or 5-second intervals

Download software– Windows-based software downloads data to a PC in ASCII

format

Lexington Travel Habits StudyLexington Travel Habits Study

Select study areaSelect study area–– A SelfA Self--Contained MediumContained Medium--Sized City: Sized City:

Lexington, KentuckyLexington, KentuckyRecruit volunteers by emailsRecruit volunteers by emails–– Staff, professors and their families at the Staff, professors and their families at the

University of Kentucky and other residents of University of Kentucky and other residents of the citythe city

ProcedureProcedure–– 12 vehicles every 2 weeks12 vehicles every 2 weeks

DateDate–– March 2002 March 2002 –– July 2003July 2003

Number of Households Number of Households ParticipatedParticipated

Total number of households surveyed = 276Total number of households surveyed = 276

Total number of valid GPS datasets = 256Total number of valid GPS datasets = 256total number of onetotal number of one--driver datasets = 124driver datasets = 124

Lexington, KentuckyLexington, KentuckyLexingtonPopulation = 250,000Population = 250,000Area = 293 Square MilesArea = 293 Square Miles

Lexington, KentuckyLexington, Kentucky

Expressways (90 miles)Arterials (308 miles)Local Streets (1058 miles)

Survey MethodologySurvey Methodology

Step 1: Volunteers are called to collect Step 1: Volunteers are called to collect demographic information such as number of demographic information such as number of people in the household, sex and age of each people in the household, sex and age of each family member, etc.family member, etc.

Step 2: GPS DataStep 2: GPS Data--Logger is installed in the Logger is installed in the volunteervolunteer’’s vehicle on Thursday or Friday s vehicle on Thursday or Friday together with an intogether with an in--vehicle booklet.vehicle booklet.

Step 3: GPS DataLogger stays in vehicle for Step 3: GPS DataLogger stays in vehicle for approximately 10 days, which includes 5 approximately 10 days, which includes 5 weekdays and 2 weekends.weekdays and 2 weekends.

Step 4: GPS DataLogger is picked up on Monday Step 4: GPS DataLogger is picked up on Monday or Tuesday.or Tuesday.

Data ObtainedData Obtained

Demographic data for each householdDemographic data for each household1010--day GPS travel data for each day GPS travel data for each householdhouseholdGIS road network database of GIS road network database of Lexington, KentuckyLexington, Kentucky

GPS Data StructureGPS Data Structure

The information recorded by the GPS The information recorded by the GPS instrument includes date, time, instrument includes date, time, latitude, longitude, speed, altitude, etclatitude, longitude, speed, altitude, etcEach dataset (household) contains up Each dataset (household) contains up to 250,000 recordsto 250,000 recordsEach record represents one GPS pointEach record represents one GPS point

GIS Road Dataset StructureGIS Road Dataset Structure

A wellA well--coded GIS network consisting coded GIS network consisting of about 13,000 separate street of about 13,000 separate street segments (or links)segments (or links)WellWell--coded roads, intersection coded roads, intersection connections, turns, oneconnections, turns, one--way, speed way, speed limit, name, type, and lengthlimit, name, type, and length

GPS Data Sample in ArcViewGPS Data Sample in ArcView

Data ProcessingData Processing

Overlay GPS points with Overlay GPS points with underlying road networkunderlying road networkSpatially join GPS points Spatially join GPS points and road links to assign and road links to assign GPS points to the road GPS points to the road links they traveled onlinks they traveled onCalculate the time Calculate the time difference difference t t and distance and distance l l between the first and between the first and the last GPS point the last GPS point assigned to a linkassigned to a linkCalculate average speedCalculate average speed

tlV /=

Data Processing (ContData Processing (Cont’’d)d)

Keep links with more than 3 GPS Keep links with more than 3 GPS points in sequence assigned to it as points in sequence assigned to it as valid datavalid data

a

bWrongly Assigned Points

c

Data Processing (ContData Processing (Cont’’d)d)

Product: Average travel speed by link Product: Average travel speed by link by personby person

Note: Note: If a link is traveled more than once, there is more than 1 If a link is traveled more than once, there is more than 1 observation. observation. Average speed including acceleration and decelerationAverage speed including acceleration and deceleration

TimeTimeAgeAgeSexSexSpeed Speed LimitLimit

Average Average SpeedSpeed

Link IDLink ID

Speed RatioSpeed Ratio

Example to calculate speed ratio:Example to calculate speed ratio:On a road link with 50 mph as the speed On a road link with 50 mph as the speed

limit and length of 1 mile, it took a limit and length of 1 mile, it took a driver 1.5 minutes to drive through. driver 1.5 minutes to drive through. The average speed is 40 mph and the The average speed is 40 mph and the speed ratio is speed ratio is --20%.20%.

%100)(×

−=

limit speedlimit speedVRatio Speed

Data SummaryData Summary

NonNon--Peak Hour Data: 8 AM Peak Hour Data: 8 AM –– 4 PM; 6 PM 4 PM; 6 PM ––6 AM6 AMTotal number of observations = 98,899Total number of observations = 98,899

Maximum speed ratio= 1.68Maximum speed ratio= 1.68Minimum speed ratio= Minimum speed ratio= --0.850.85Average speed ratio= Average speed ratio= --0.250.25Standard Deviation speed ratio = 0.22Standard Deviation speed ratio = 0.22

Number of different links = 5421Number of different links = 5421Average observations per link = 19Average observations per link = 19

Significant Factors Affecting Significant Factors Affecting Speed RatioSpeed Ratio

Speed limit Speed limit –– 25, 35, 45 and 65mph25, 35, 45 and 65mphSex of the driverSex of the driverAge of the driver Age of the driver

Age group 1: 21Age group 1: 21--3030Age group 2: 31Age group 2: 31--5050Age group 3: 51Age group 3: 51--6565Age group 4: > 65Age group 4: > 65

Number of ObservationsNumber of Observations

1313121227272222282815153344NumberNumberMMFFMMFFMMFFMMFFSexSex

> 65> 6551 51 -- 656531 31 -- 505021 21 -- 3030AgeAge

Distribution of Speed RatiosDistribution of Speed Ratios

¼ Positive and ¾ Negative

Median of the Speed Ratio of Median of the Speed Ratio of Different Age GroupsDifferent Age Groups

MediumMedium--ages fasterages fasterOlder females slower Older females slower

Median of the Speed Ratio on Median of the Speed Ratio on Different Types of Road LinksDifferent Types of Road Links

Expressways higherExpressways higherFemales slower Females slower

Median of the Speed Ratio on Median of the Speed Ratio on Roads with Speed Limit of 25 Roads with Speed Limit of 25 and 35 MPHand 35 MPH

MediumMedium--ages fasterages fasterOlder females slowerOlder females slowerYounger females faster Younger females faster

No obvious difference No obvious difference

Median of the Speed Ratio on Median of the Speed Ratio on Roads with Speed Limit of 45 Roads with Speed Limit of 45 and 65 MPHand 65 MPH

Younger slowerYounger slowerOlder women slowerOlder women slower

No obvious difference No obvious difference

Median of the Speed Ratio of Median of the Speed Ratio of Age Group 21Age Group 21--30 and 3130 and 31--5050

Females faster on localFemales faster on localNo obvious difference other casesNo obvious difference other cases

Arterials slowerArterials slowerExpressways and locals fasterExpressways and locals faster

Median of the Speed Ratio of Median of the Speed Ratio of Age Group 51Age Group 51--65 and > 6565 and > 65

Arterials slowerArterials slowerExpressways and locals fasterExpressways and locals fasterFemales slower on expresswaysFemales slower on expressways

Females slower on locals and Females slower on locals and expresswaysexpresswaysExpressways higherExpressways higher

Speed Ratio on Local StreetsSpeed Ratio on Local Streets

Speed Ratio on Arterials and Speed Ratio on Arterials and ExpresswaysExpressways

Spatial Distribution of the Spatial Distribution of the Speed RatiosSpeed Ratios

Low speed in downtown areaLow speed in downtown areaRelatively high speed on circle roads Relatively high speed on circle roads and expressways outside of the town and expressways outside of the town centercenterLow speed on ramps and interchangesLow speed on ramps and interchanges

GPS is very effective in collecting GPS is very effective in collecting speed data of individual driver.speed data of individual driver.Women are driving slower than men in Women are driving slower than men in most cases. This trend is more most cases. This trend is more obvious in some age groups than obvious in some age groups than others. others.

ConclusionsConclusions

Conclusions (ContConclusions (Cont’’d)d)

Young drivers, at least young drivers Young drivers, at least young drivers in Lexington, are not necessarily more in Lexington, are not necessarily more aggressive than older people. An aggressive than older people. An alternative reason for this is that alternative reason for this is that young drivers are more cautious about young drivers are more cautious about driving with GPS devices on board. driving with GPS devices on board. The relatively The relatively small samplesmall sample size of size of young drivers is another young drivers is another explanation.explanation.

Next StepsNext Steps

Peak travel Peak travel Cruise speedsCruise speedsAcceleration/Deceleration pattern for Acceleration/Deceleration pattern for emission studyemission study

Thank you!Thank you!