Draft Spot Speed Study Training

8/6/2019 Draft Spot Speed Study Training

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What is a Spot Speed Study?

Spot speed studies are used todetermine the speed characteristics

of a traffic stream at a specificlocation along the roadway.


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Why Spot Speed Studies? Determine existing roadway speeds

Evaluate effectiveness of speed enforcementprograms

Identify the speed impact of roadwaygeometry and roadway features

Determine impact on speed of traffic control

devices

Provide evidence to support/refute excessive

speed complaints


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Spot Speed Study Steps

STEP 1. Organize Study Plan

STEP 2. Select Data Collection Technology

STEP 3. Select Appropriate Site and CollectField Data

STEP 4. Reduce and Analyze Data

STEP 5. Interpret and Report Findings


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Time and Date Selection

Recommended:

Late spring orearly autumn

Tuesday,Wednesday orThursday

Reflect normal driving conditions

Not Recommended:

Unique events

Inclement weather

Holidays

Peak travel times


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Location Selection

Recommended:

Free flow conditions

Uniform roadway

segments

Reflect normal driving conditions

Not Recommended:

Traffic signals andother junctions

Intersections

Curves Work zones

Parking zones

Active crosswalks


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STEP 2. Select Data Technology

HandheldTechnologies Equipment manuallyoperated

In-RoadTechnologies

Equipment installed inor on roadway

Out-of-RoadTechnologies

Equipment installedoverhead or on side of

roadway


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STEP 2. Select Data Technology

In-RoadTechnologies


HandheldTechnologies

PneumaticRoad Tubes

Magnetic

Sensors

Inductive

Loops

Radar LiDAR

CountBoards

Microwave Ultrasonic

Acoustic

Infrared

Multiple

technologies

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Handheld Technologies

Handheld radar or LiDAR meters toidentify vehicle speeds

Speeds are recorded manually on a datasheet

Minimum data requirements must be met

to ensure quality of data

Efforts must be made to reduce bias

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In-Road Technologies

Disruption of traffic flow duringinstallation and maintenance

Safety concerns for operating in the road

Maintenance issues:

Snow removal, street sweepers

Heavy vehicle traffic

Typically well established technologies

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Out-of-Road Technologies

Limited or no disruption of traveled way Typically newer technologies

Typically more expensive than in-road

Some have complex installation processes

Maintain the traveled way

Increased Safety

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STEP 3. Collect Field Data

Materials Preparation Prepare inventory sheetDate, location, speed limit

Understand how to use recorder Gather equipmentData sheets

Pen or pencils and something to write on

Safety equipment

Tape measure

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STEP 3. Collect Field DataSite Setup:

In-Road and Out-of-Road Technologies Adequate number of people to setup

equipment and monitor traffic Equipment or vehicles out of stream and

out of driver view

Document layoutSite setup sketch

SAFETY! SAFETY! SAFETY!

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Additional Safety Considerations

During installationBeacons or flashers

Cones or warning signs

Reflective vests

One person to monitor traffic

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STEP 3. Collect Field Data

Place a tick mark for

vehicle observed

Column Vehicle type

Row Speed

Bus at 32 mph

Data Collection Sheet:

Radar or LiDAR

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Parameters associated with roadway speedsMode

Mean Speed

85th Percentile Speed

95th Percentile Speed

Median (50th Percentile Speed)

Speed Variance

Pace

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1. Tick marks from datacollection

2. Count and record tickmarks for each type ofvehicle

3. Count and recordvehicles at eachspeed

4. Count and record totalvehicles in survey


Radar or LiDAR

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Mode: 29 mph


Radar or LiDAR

Most frequentlyobserved speed

26 observations

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Mean Speed:N

Sn

Si

ii=

Si:observed speed group i

ni: number of observations for

speed group i

N: total number of observations


Radar or LiDAR

Si

ni

N mph29250

)143(...)620()229( =+++

Mean Speed for passenger cars =

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Pace: 25 to 35 mph


Radar or LiDAR

10 mph window thatencompasses the highest

portion of observed speeds175 observations

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1. Cumulative frequency

Number of observations ator below the given speed

2. Cumulative percent

Percentage of speeds at orbelow the given speed

Data Analysis Sheet:

Radar or LiDAR1 2

CumulativeFrequency

Number ofobservations

=

Cumulative

Percent

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STEP 4. Reduce and Analyze DataData Analysis Sheet:

Radar or LiDAR

50th Percentile

Speed: 29 mph 85th Percentile

Speed: 34 mph

95th PercentileSpeed: 37 mph

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Frequency DistributionsNormal Cumulative


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STEP 5. Interpret and Report Findings

Community Meeting Presentations

Educational Materials for Neighborhoods

Information for community policy makers(Town Council, Traffic Committee, etc)

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Types ofTechnology

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Handheld Technologies

Radio Detection andRanging

Wide field of viewprogrammed to reportstrongest or fastest

vehicle Not effected by

inclement weather

Radar

Light Detectionand Ranging

Narrow field of view more selective oftargets

Can be programmedto Ignore inclement

weather Shoot through glass

LiDAR

Prefer

red

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In-RoadTechnologies

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PneumaticAir pulses sent to classifier used to classify passingvehicles well suited for low volume roads.

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Pneumatic

Easy Installation

Low initial price

Simple to maintain

Low power usage

Installed on trafficway

MaintenanceVandalism/wear

Snowplows/StreetSweepers

Weather

Sensitive to coldWater in tubes

Advantages Disadvantages

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PneumaticLayout


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Magnetic

Some offer easyinstallation

High accuracy(speed)

Cant detect stoppedvehicles

Some have smalldetection zone

Installation in trafficway


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Magnetic

Layout

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MicrowaveRadio waves bouncing back from a target vehicle

have a change in frequency corresponding with therelative speed of the vehicle (Doppler Effect).

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Microwave

Simple installation

Sidefire or overhead

Not in trafficway

Not effected byweather

High accuracy

Multilane option

Costly

Cant detect stopped

vehiclesOverheadexisting

structure for mounting

Installationrequirements must besuitable forapplication


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MicrowaveInstallation

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Ultrasonic

Measures Doppler Effect to detect vehiclespeed (similar to microwave).

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Ultrasonic

Not installed intrafficway

Simple installationOverhead as sidefire

reduces accuracy

Multilane option

Mid-priced

Effected by someenvironmental factors

Temperature changeExtreme air turbulence


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AcousticMeasures the acoustic energy from vehicles.

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Acoustic

Multilane option

Not installed in

trafficway 2 hour installation

Sidefire

Insensitive toprecipitation

Average accuracy

Effected by coldweather

Effected by outsidenoise

Some cant be used

with slow or stop-and-go traffic


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AcousticInstallation

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Infrared

Vehicles are illuminated by two beams of low powerinfrared light and the time it takes to cross the twobeams is used to calculate vehicle speed.

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Infrared

Measures vehicleposition, speed, class

Multilane option Not installed in

trafficway

Overhead becausesidefire reducesaccuracy

Lane coveragelimited to 1-2 lanes

Short range Vehicle classification

on height not length

Effected by weatherFog or heavy snow

Costly


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Infrared Installation

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Multiple Technologies

Combines out-of-road technologies

+PassiveInfrared Radar/Microwave Ultrasonic.+

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Multiple Technologies

Can be used basedon best for task

Easy installation

Improved accuracy

Mid-priced can bemore expensive thanother technologies


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MultipleTechnologies

Installation

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For more information

Caroline Hymoff

Governors Highway Safety Bureau

(617) 725-3334

[email protected]

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Questions?

Draft Spot Speed Study Training

Documents

Transcript of Draft Spot Speed Study Training