bp gfor sttc_oct_26_2011

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Best Practice Guide for Short Term Traffic Surveys

October 2011

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5.5 New Sites To allocate a new site

1. Step 1.

2. Step 2.

3. Step 3.

4. Etc.

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5.6 Special Note for Speed Surveys Most traffic studies will only require a survey at one point on any traffic section. Speed surveys, on the other hand, may attempt to characterise speed at various points along a given traffic section.

Fix X – Speed Surveys Diagram showing speed survey sites allocated to multiple points within a traffic section, with precise definition of SLK at each site (to facilitate any repeat surveys).

Careful liaison with stakeholders is crucial to the success of speed surveys, to ensure that the sites planned meet their information needs.

Accurate site identification is also very critical for enforcement purposes and for follow-up studies.

Note: To facilitate later site identification for speed surveys, it may be necessary to included additional information in the Site Description, e.g. nearest house number or other significant feature.

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6 Site Selection Site selection is the process of identifying the physical location for placing traffic survey loggers and sensors. Whilst site placement considerations are an integral part of survey planning, the selection of actual survey sites should be regarded as a separate process.

Site selection is almost always performed in the field by the Survey Supervisor or by others sufficiently familiar with short term traffic surveys and the goals of the particular traffic study.

When selecting physical survey sites, several factors must be considered, including:

Safety and ease of installation.

Data quality.

Information needs of the survey program.

Prior to commencing any equipment installation, the Survey Supervisor must review and approve the selected locations.

6.1 Volume Counting In the context of this Guide, volume counting is the process of gathering only indicative vehicle volumes using a single sensor installed across the lane or carriageway. Traffic volume counting is generally only performed in circumstances where site constraints prevent the gathering of classified vehicle data and where vehicle classifications and speeds are not required.

6.2 Vehicle Classification In the context of this Guide, vehicle classification is the process of gathering vehicle classification and speed data using paired sensors.

Vehicle classification surveys are preferred where possible, as they provide the maximum vehicle information.

6.3 Characteristics of Suitable Survey Sites

6.3.1 Safety Visibility. Approaching drivers must be able to clearly see the installers, and installers must have

an unobstructed view of any oncoming traffic.

Pedestrian and cyclist safety must not be compromised by any short term traffic survey. Sensors must not be installed across footpaths.

Note: Sites must be selected to allow for the safe installation of survey instruments and sensors. This requirement takes precedence over any other requirement.

Note: UNDER NO CIRCUMSTANCES are surveys to be carried out where tubes are required to traverse footpaths or bicycle paths.

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6.3.2 Escape Routes Installers must be physically able to exit the roadway without obstruction.

Sites must be selected so that installers have at least two escape routes.

Note: UNDER NO CIRCUMSTANCES are surveys to be carried out where installers would be required to negotiate any obstacle (eg guard rail, barrier fencing) to exit the road way.

Note: Narrow median islands are not considered to be a safe refuge.

6.3.3 Road Condition The road must be in suitable condition to retain any fasteners (nails, screws) being used to retain

the sensors (tubes) for the survey duration.

Road surface must allow installers to affix the sensors without excessive effort or delay. Concrete pavements may require pre-drilling.

Avoid any areas of severe rutting, potholing, significant change of grade or other road damage. Poor road condition may affect driver behaviour and vehicle performance, spoiling the validity of road usage data at the affected point.

Sites on bridge decking will require engineering permission before any installation.

6.3.4 Road Geometry Avoid selecting sites where vehicles are altering their trajectory.

Avoid selecting sites where vehicles are entering and exiting side roads or driveways

Note: Vehicles crossing the sensors at a non-perpendicular angle may be recorded with an incorrect speed and wheelbase.

6.3.5 Traffic Conditions When selecting a site that is representative of an entire traffic section, ensure that vehicles are free-

flowing and travelling at the maximum speed for that particular section.

When selecting sites, the possibility of kerbside parking needs to be considered. Avoid locations where parked cars may impact normal road usage.

Avoid locations with excessive queuing. Surveys during periods of heavy congestion or queuing will usually result in poor quality data.

6.3.6 Anchor Points Select sites with suitable anchor points for securing roadside data loggers. Trees, power poles, guide signs may be suitable anchor points.

An eye bolt or a secure picket or post may be installed temporarily to provide a suitable secure anchor point.

Fig X. Sign used as anchor

Fig X. Temporary eye bolt anchor

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Note: Smaller signs (e.g. Keep Left) may not provide adequate security.

Note: Avoid anchor points in roadside culverts if flooding may occur during the survey period.

Note: UNDER NO CIRCUMSTANCES should any of the following be used as anchor points:

Private property (e.g. letterboxes, garden ornaments).

Pedestrian facilities (e.g. grab rails).

Drains, gratings or access covers.

Any object within a rail reserve.

Note: When selecting anchor points, be aware of:

Any possible interference.

Potential for vandalism that may result in loggers being placed in hazardous positions.

Pedestrian behaviour in the vicinity.

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6.4 Lane Numbering at Multi-lane Vehicle Classification Sites Nearly all vehicle classification surveys are carried out at sites comprising more than one lane, and are therefore performed using multiple loggers. Yet the site ID almost always refers to all lanes at the survey location. Therefore, a unique lane number must be assigned to each lane to distinguish data gathered from each logger used at the same site.

To Establish Unique Lane Numbers

1. Determine the road’s primary direction for the traffic section or location to be surveyed.

2. Facing towards the primary direction (North or East), sequentially number each lane from the left, starting with Lane 1.

When selecting survey locations for multi-lane sites, consideration needs to be given to the placement of all loggers required to survey the entire site.

Note: The lane numbering method as described above is different from the method used elsewhere in Main Roads, to ensure that each logger has unique Header information.

6.5 Single Carriageway Bidirectional Vehicle Classification Sites

There is no rule-of-thumb for when a single logger can be used for vehicle classification surveys of bidirectional traffic. If the occurrences of two vehicles simultaneously crossing the tubes is very low, then data quality will be very good. As the number of simultaneous crossing events increase, data quality will decrease. It is a matter of assessing the convenience of a single unit, against the acceptable data quality for any given site.

Fig X. Lane Numbering

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6.6 Multi-lane Uni-directional Vehicle Classification Sites Note: UNDER NO CIRCUMSTANCES should a single logger be used to gather vehicle

classification data at multi-lane uni-directional sites. Data gathered in this manner will frequently contain many errors due to simultaneous vehicles travelling in the same direction.

6.7 Site Marking Site marking is recommended for:

Large and complex surveys.

Precise logger placement for location-critical studies (i.e. speed surveys).

Surveys in metropolitan and built-up areas.

Sites scheduled for repeat or follow-up surveys.

Surveys where logger installation must occur at night.

Site marking should only be carried out at sites after approval by the Survey Supervisor.

Adequate site marking will unambiguously identify the survey location.

Equipment installers must be familiar with any site marking and be readily able to locate any marked sites.

Note: It is recommended that sites be marked with a green raised pavement marker placed in the carriageway, with the Site ID stencilled with yellow paint adjacent to the edge line.

Note: Raised pavement markers may only be placed in accordance with Main Roads guidelines.

Fig X. Site marked with yellow stencilled paint

WARNING – DO NOT install paired tubes for vehicle classification surveys across two or more lanes with the same flow direction. This will result in erroneous classification data.

Fig X. Site marked with green marker

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7 Equipment Installation 7.1 Safety Notice – Traffic Volume Limits Note: UNDER NO CIRCUMSTANCES should short term traffic survey equipment be installed on

any carriageway during periods when individual lane volumes exceed 100 vehicles per hour. Installing tubes on high volume and high speed roads may pose significant risks to installers and other road users.

Note: All traffic surveys must be carried out with appropriate traffic management.

Note: If available, previous traffic counts in the vicinity may provide a guide as to whether lane volumes exceed 100 vehicles per hour during the proposed installation period.

7.1.1 Night-time Installation As traffic data is frequently required from roads with high traffic volumes, it is often necessary to schedule short term traffic survey equipment installations at night when vehicle flows have subsided.

7.2 Traffic Management Traffic management must be in accordance with all standards.

7.2.1 SpotterWhen installing short term traffic counting equipment, it is recommended that one installer act as a spotter to warn of dangerous situations. The spotter must be continuously monitoring approaching traffic whilst other installers are on or near the road.

7.3 Vehicle The installers’ vehicle is an integral safety component. It must be equipped with rotating or flashing yellow beacons that remain visible to approaching traffic at all times during equipment installation, including logger setup at the roadside.

7.4 Safety Equipment Installers must wear appropriate personal protective equipment, including protective footwear and high visibility jackets, when working on or near the road.

Note: UNDER NO CIRCUMSTANCES should installers exit the vehicle prior to equipment installation if not already wearing an approved high visibility jacket.

Protective gloves and eyewear must also be worn when required.

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7.5 Traffic Survey Equipment

Traffic data logger

Logger must have sufficient battery life and memory for the expected or required survey duration.

Compatible notebook or netbook computer

Installed with latest logger operating software.

A 12 volt car charging adaptor is recommended.

Ruggedising kits may be available for added durability.

Communications cable

Compatible with traffic data logger.

Connects computer to logger for setup, data unload and other logger operations.

Rubber pneumatic road tube sensor

Secured to the road to detect passing axles.

Available in 30m rolls or 100m spools.

Road nails

50mm hardened nails specifically for traffic surveys, not suitable for gravel roads.

Galvanised deck spikes may provide sufficient anchorage for gravel roads.

Cleats

Suitable for fastening Rubber pneumatic road tube sensor, maintaining the required tube tension for the survey duration.

“Figure-8” cleats (illustrated) are preferred, being light yet sufficiently durable for most traffic surveys.

Centre-lane flaps

To provide additional sensor stability and durability.

May be used as a saddle over the tube, using two nails, or folded over the tube and secured with one nail.

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Textile-backed bitumen tape (“Bitulastic” tape)

An alternative to centre-lane flaps, cut to the desired length.

Used as saddles over the tube.

Only suitable for dry road conditions.

Note: Bitumen tape does not replace the use of cleats, as it does not maintain tube tension.

Bitumen tape must be thoroughly amalgamated with the road surface.

7.5.1 Other Items

Spare battery packs

Available from logger manufacturer.

Only use recommended battery packs.

Hex ball driver

For opening logger to replace battery.

Padlock, chain or security strop

For anchoring and securing logger at survey location.

7.6 Installation Tools Tape measure or calibrated spacing gauge.

Chalk or lumber crayon.

Sharp knife or side cutters.

Heavy Duty Claw Hammer, heavy ball hammer or heavy mallet.

Crowbar.

A cordless drill with interchangeable screwdriver bits may be required for concrete roads.

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7.7 Sensor Configurations – Vehicle Classification For short term traffic surveys where actual vehicles are required with class and speed information, paired tubes are installed with a precise spacing. Almost always, paired tubes are installed in each lane, with full site coverage requiring a logger for every lane.

Single lane

Paired tubes installed across a single lane.

Two lane bidirectional

Paired tubes installed across a two-lane bidirectional carriageway.

Note: A single logger can be used for bidirectional traffic only if the occurrences of two simultaneous vehicles crossing the tubes is very low.

Two lane – separate tubes

Paired tubes installed in each lane.

Can be used for any flow direction.

Used at sites where anchor points are widely separated on opposite sides of the carriageway.

Two lane – shared tubes

Shared paired tubes installed across two lanes.

Knots at the centreline isolate each lane.

Simplifies installation at multi-lane sites.


Can only be used at sites where anchor points are closely spaced on opposite sides of the carriageway.

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7.7.1 Blocker or No-Count Tubes Specialised non-compressible tubes, often referred to as “blocker” or “No-count” tubes, are available to isolate lanes, by masking the axle hits in the near lanes. Blocker tubes allow surveys at multi-lane sites where anchor points are unavailable for the lane being surveyed. Examples:

Four lane road with no central median, or

Carriageways with three or more lanes.

Two lane – “blocker” or “No-count” tubes

Paired tubes installed in each lane.


Used at sites where anchor points are only available on one side of the carriageway.

Blocker tube can be extended into other lanes (eg three loggers covering three lanes).

Note: Blocker tubes may be difficult to install and may not remain non-compressible for the survey duration. Special tools may also be required for installation – check with the manufacturer. Furthermore, additional traffic control will generally be required, with longer installation times across multiple lanes.

7.7.2 Vehicle Classification – Installations to Avoid

Two or more uni-directional lanes

Error prone.

Tends to overestimate heavy vehicles.

Crossover

Difficult to install.

Very error prone.

Not supported by software.

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7.8 Sensor Configurations – Volume Counting For short term traffic counting where only indicative volumes are required, a single tube may be installed across the lane or carriageway. Further lane or carriageway differentiation can be obtained using a second tube.

Single tube

May be installed across any number of lanes or the entire carriageway.

Provides indicative traffic volume only.

Dual tube – “Split” configuration

Short tube – long tube combination allows directional or lane-based indicative traffic volumes.

Volume in the far lane (i.e. the lane covered only by the long tube) is derived using software by subtracting short tube counts from the long tube counts.

Dual tube

Logger installed in the median.

Two tubes, one per lane or carriageway, provides indicative volumes of each direction.

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7.9 Installation Procedure The following section discusses the installation of a logger using a classification tube layout. The tips and techniques discussed here can be carried over to traffic count layout installations.

7.9.1 Typical Tube Layout – Separate The following diagram depicts a generalised tube configuration for use with a single logger.

FigFig-8 cleats

7. Separate Tube Centre-lane flap

(used as a saddle) Centre-lane flap

(used folded) Textile-backed bitumen tape

Fig-8 cleats Knots

Fig 8. Separate Tube Layout

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7.9.2 Typical Tube Layout – Shared The following diagram depicts a generalised tube configuration for use with a two loggers, one at each end.

FigFig-8 cleats

9. Shared Tube Knot (or

other airtight blockage)

Knot (or other airtight

blockage)

Fig-8 cleats

Fig

To attach a Figure-8 Cleat

10. Shared Tube Layout

1. Place one end of the pneumatic tube over the large loop of a Figure-8 Cleat.

2. Twist the Figure-8 Cleat to form a second loop, and slide over the end of the pneumatic tube.

3. Bunch the two loops together, and pull the tube through as required.

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To install pneumatic tubes (suggested method)

1. Prepare two tubes of equal length, and sufficiently long to cover the required lanes, and reach the logger securing point.

2. Using a tape measure, or one meter stick, mark the one meter tube spacing on the road with a lumber crayon or chalk.

3. Attach Figure-8 Cleats to one end of each tube, using one or two per tube.

4. Seal the same end of each tube with two knots, adjacent to the cleats.

5. Secure both tubes to the road, using a road nail through the eyelet of each cleat.

6. Attach Figure-8 cleats to the curb side of each tube, using one or two per tube, and secure to the road using road nails. Ensure that the tubes are parallel to each other, and perpendicular to the direction of vehicle travel.

7. Double-check that the tube spacing is one meter.

8. Stretch each tube 10% to 15% to minimise lateral movement. Use a cable tie around the curb side cleats if necessary to prevent slippage.

9. Ensure that the tube length from the wheel path to the logger’s air sensors is exactly the same. A difference in length will result in incorrect speeds and wheelbases.

10. Attach canvas flaps as required using two road nails per flap. This will minimize lateral movement over long distances. Using one in the centre of each lane, in addition to between two lanes will maximize data quality. Short lengths (8 – 10cm) of textile-backed bitumen tape can be used as an alternative.

11. Remove the logger’s inner tray from the stainless steel case and feed both tubes up through the handle.

12. Place the PVC main system unit next to the tray and attach each tube to the appropriate air sensor. Remember to use the convention of the A tube being the first hit by a vehicle travelling in the lane closest to the logger. Use the logger’s Status LEDs, or the Traffic View on a mobile PC, to verify the correct tube connections.

13. Place the PVC main system unit into the tray, and push each tube into the tray's respective locking cut-outs, as shown in the diagram below.

Fig X. Spacing tubes with gauge

Fig X. Centre flap as saddle

Fig X. Centre flap used folded

Fig X. Bitulastic tape used as saddle

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14. Slide the tray into the outer case, and secure the logger using a padlock through one of the holes in the handle.

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7.10 A Final Checklist There are four major items to be checked when installing road tubes for classification surveys.

When installed, tubes must be:

Correctly spaced.

Parallel to each other.

Perpendicular to the direction of vehicle travel.

Equal length from wheel path to logger. This must be checked after tensioning the tubes.

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8 Logger Setup To operate MC5600 logger, a notebook or netbook computer running MTE will be required. MCSetup is the component of MTE used to interface with the MC5600 and is used for all logger operations.

The MC5600 records every axle strike, regardless of the survey requirements. Operating the MC5600 is therefore very simple, only requiring setting of the logger’s header details.

The following display is the start up screen for the MCSetup application.

With MCSetup, the large buttons are used to perform the following tasks:

Other logger diagnostics are available in the menu.

Check the status of the logger;

Setup the logger to start a new survey;

Unload data from the logger, including dynamic graph of axle hits;

View vehicles and axle hits in real-time to verify sensor installation;

Change data channels – not used with the MC5600.

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8.1 MCSetup’s Preferences MCSetup’s Preferences Dialog Box

Preferences will need to be set when starting MCSetup for the first time.

To change Preferences at any time,

Choose View menu » Preferences.

Use MCSetup ‘Preferences’ to select communications port. In the event that MCSetup will not communicate with the logger, check the comms port in ‘Preferences’.

Choose the folder where unloaded data will be stored, then use the buttons for further sub-grouping. MCSetup will create folders for you if they don’t already exist.

MCSetup uses a combination of site ID, plus day and month of unload to create unique dataset names. Choose ‘long file names’ to create long Windows-only file names.

Base folder

Further sub-folders, created automatically during unload

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8.3 Checking the Logger

The status dialog box in MCSetup displays a snapshot of the logger’s current status.

The dialog box pictured below opens when clicking on the RSU Status button, displaying status information. The status information is divided into five pages: Data, RSU, Battery, Sensors and Memory. It is recommended to conduct a logger status check during a survey to review the data collected and detect if any potential problems may arise.

8.3.1 Data Page The Data page displays the information entered into the logger during setup. Details here are covered later in the Setup section.

8.3.2 RSU Page The RSU page contains information about the logger’s status. The ‘Ident’ field displays the logger’s unique serial number. ‘Status’ text is important and should be noted when checking a logger’s status.

Watch the Status text change after performing Setups and Unloads, etc.

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8.3.3 Battery Page The Battery page displays the logger’s voltage of the non-rechargeable alkaline battery pack. Battery life remaining is based on current consumption, and the battery pack’s discharge characteristics, which is active for 290 days. Typically a MC5600 logger will stop logging once the alkaline battery is reduced to 4.8 volts.

Note that the RAM backup battery receives its power from the main battery, and should always remain in the “green” zone.

8.3.4 Hits Page The Sensors page shows information about the axle hit data currently in the logger’s memory. For classifier surveys an A/B ratio of between 95 – 105% is acceptable. If there is a problem with the sensor balance, MCSetup will issue a warning when clicking the RSU status button.

8.3.5

Watch for sensor imbalance, which may indicate tube faults

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Memory Page The Memory tab displays a graphical representation of the logger’s memory. When the logger’s memory is full, it will stop recording axles. The Memory page contains a run-time estimate to be used as a guide.

8.4

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8.5 Logger Setup Note: Before commencing a new survey, check that the computer’s date and time is correctly set.

MCSetup’s Setup dialog box allows you to quickly setup for a new survey:

MCSetup Header Field Values to be entered or selected Site The site ID from the Reporting Centre. Up to 5-digits, zero-filled (e.g. 00123).

Attribute Optional. May be set to the current latitude and longitude if obtained from an optional GPS unit.

Operator Operator’s initials.

Start time Set to start immediately, on the next hour, midnight tonight or defer to midnight Sunday.

Site description The site description from the Reporting Centre. May include the site’s posted speed limit in angle brackets, eg <60>. If used, append the posted speed limit to the end of the Reporting Centre’s description.

Sensor layout Choose either “Paired” for classification surveys, or the other options for traffic counts.

Lockout Choose Lockout from the menu (usually either 10ms or 30ms).

Direction Choose the flow direction over the tube (see note below).

Lane Set to “0” for two lane bi-directional classification sites, otherwise number each lane separately as described in the section on “Lane Numbering”.

Spacing Click “Set spacing” to enter physical tube spacing, checked and verified beforehand.

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Note: For classifier layouts, choose a Direction that characterises the flow directions over the tubes. For volume layouts, choose the flow over each tube separately.

Note: The logger’s tube inputs (i.e. the brass spigots) are clearly labelled ‘A’ and ‘B’. The tubes only assume their ‘A’ or ‘B’ identity after connecting the tubes to the logger.

Fix X – Notebook computer being used to setup MC5600 logger

8.6 Example Site Descriptions The following tables give examples of acceptable site descriptions, and some common descriptions that are not compatible with Reporting Centre.

Table 3. Descriptions compatible with Reporting Centre

Example Description Notes Great Eastern Hwy E of Belgravia St Acceptable site description

Great Eastern Hwy E of Belgravia St <60> 60 km/hr posted speed limit appended in angle brackets

Great Eastern Hwy E of Belgravia St, 4.36 SLK Although not strictly required, SLK can be used for precise site location, e.g. for speed studies. (Note: SLK is linked to the unique Site ID in Reporting Centre).

Table 4. Descriptions NOT compatible with Reporting Centre

Example Description Notes

Great Eastern Highway E of Belgravia Street Full road designations are not required. Instead, use standard abbreviations.

GREAT EASTERN HWY E OF BELGRAVIA ST All capitals is not required. Instead, use upper and lowercase letters.

H003 GEH E of Belgravia St Main Roads’ road designations and other road abbreviations are not required. Instead, use gazetted road names.

Great Eastern Hwy east of Belgravia St Full compass direction from nearest intersection is not required. Instead, abbreviate as “N”, “E”, “S” or “W”.

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9 Mid-Survey Checking Mid-survey checking is recommended for:

Surveys of seven or more days duration; or

Surveys providing critical data for stakeholders.

Checking can simply be a quick drive-by to ensure that the tubes are intact. More detailed inspection may be required for critical surveys.

Note: If a mid-survey data snapshot is required, the logger may be unloaded, but with logging continuing.

9.1 Monitoring a Survey

During a survey it is advisable to regularly check your site to ensure that any loss in data quality is detected before a survey is completed.

Note: Remember MC5600 loggers store every axle hit. Traffic views in MCSetup are therefore transient representations of the actual data and MUST BE USED WITH CAUTION.

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10 Data Unload

Uncheck “Stop the RSU after unloading data” to unload the data so far, but continue data gathering (i.e. for a mid-survey checking).

Check “Stop the RSU after unloading data” to complete the survey.

Note: DO NOT change the file extension (eg ‘EC0’, ‘EC1’, etc). Changing the default file extension will make it impossible of other MetroCount programs to locate and identify files.

Note: After unloading data, including the option to “Stop the RSU after unloading data”, the data is retained in the logger until the next setup.

DON’T CHANGE THE DEFAULT FILE EXTENSION

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10.1 Data Quality Check During Unload The easiest method of performing a data quality assessment mid-survey is to perform an Unload without stopping the RSU. This will leave the logger active, while still displaying the A and B tube hit plots as the data transfers.

Watch the sensor balance plot as your data unloads. Immediately spot sensor imbalance, indicating a possible tube fault.

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11 Equipment Removal Equipment removal is simply the reversal of the physical installation process.

As with equipment installation, the same requirements apply with respect to safety, traffic control, traffic volume limits, etc.

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