SECTION 642 - MAGNETOMETER DETECTION SYSTEM (MDS)
642.01 Description. This work consists of furnishing all components and materials
required to enable a wireless, battery-powered Magnetometer Detection System that detects vehicles and bicycles on a roadway using battery powered magnetometer type sensors with wireless communications to transmit detection information. The system shall detect vehicles on a roadway using only changes in the earth’s magnetic field and provide detection outputs to a roadside master device before the data is relayed to a freeway cabinet, a local traffic controller cabinet, a Central Software System, and/or data server as required as required by the application. The application of the MDS shall be shown in the plans or project specifications. These specifications cover both intersection presence-based vehicle detection used for traffic controller input, as well as freeway system or advanced system detection data collection of volume, occupancy and speed. This specification sets forth the minimum requirements for the system. The detection system shall provide accurate roadway data as needed to support the traffic management application. All wireless, battery-powered Magnetometer Vehicle Detection Systems (MDS) shall consist of one or more battery-powered wireless Vehicle Sensor Nodes (VSN) installed in-pavement with reusable enclosure. The MDS may also consist of one (1) or more Repeaters (RPs) mounted on poles on the side of the roadway. The MDS shall also consist of either: • One (1) or more Access Points (AP) mounted on the side of the roadway, one (1) or more Access Boxes, and one (1) or more Contact Closure Interface Card(s) (with Expansion Card System (EX) if required); or • One (1) or more Access Point Contact Cl osure (APCC) Interface cards (with an Expansion Card System (EX) if required), one (1) or more Isolator Modules (ISO), and one (1) or more Serial Port Protocol Digital Radios (DR) mounted on the side of the roadway; or • Equivalent system as approved by the Engineer The MDS may also include In put/Output (I/O) Modules if Access Point Contact Closure cards are used. All MDS shall also include CAT6 Outdoor Ethernet Cable, Epoxy Sealant for installation, and applicable operating an d configuration software. Software shall operate on a conventional laptop PC. Communications between the sensors and the DR or RP and between the RP and DR or another RP shall be via radio. Detection data shall be relayed using contact closure signals. Data shall be capable of being relayed to a Central Software System or central server over standard IP networks. The MDS shall also include any incidental items necessary for a complete and operable unit in place and accepted.
642.02 Materials.
642.02.1 Functional Capabilities. The VSN shall detect a vehicle by measuring a change
in the x, y, and z axis components of the earth’s magnetic field near the VSN caused by a stopped or passing vehicle. The VSN shall communicate the detection information to the AP, DR, or RP via wireless radio. The VS N shall transmit detection information within 150-ms of a detected event. The VSN shall communicate time-stamped ON and OFF vehicle detection events. The VSN shall auto matically re-transmit a detected event if no acknowledgment is received from the AP or APCC/DR. The VSN shall automatically recalibrate in the event of a detector lock. If radio connection is lost due to stopped vehicles near the VSN, each VSN shall be capable of re-establishing radio link with supporting AP or APCC/DR or RP in less than two (2) seconds. Each MDS system shall consist of one
1.or more VSN’s located as identified on the plans. Communications between a VSN and DR or AP can be direct, via a single re peater, or via two (2) repeaters operating in tandem. The Radio Frequency (RF) link among the AP, DR, RP, and VSN shall conform to the following: • The RF link shall utilize an IEEE approved wireless communications protocol. • The center frequencies, bandwidths, and tr ansmit power levels of the radio links shall allow operation in an unlicensed frequency band. • Frequency channels which are user configurable shall be employed by the sensors, APs or APCCs and RPs to avoid interference with other devices operating in the unlicensed band. • The AP or DR to VSN (or RP to VSN) RF range shall be at least 150 feet for an DR/AP/RP installed at 20 feet above the ro adway and at least 125 feet at 18 feet above the roadway. • The RP to AP or DR RF range shall be at least 750 feet when both units are installed 18 feet above the roadway with clear line of sight. For freeway applications and where advanced system detection is provided, per the plans and specifications, detection data shall be rela yed to a central software system or central server. In this case each installation of the wireless, battery-powered Magnetometer Vehicle Detection System shall provide the following measurements, as required by the application: • Vehicle volume (count) per lane over a specified time interval • Lane occupancy (percent) over a specified time interval • Vehicle speed (mph or kph) when more than one sensor is deployed in a lane o Per-vehicle speed o Median speed over a specified time interval o Mean speed over a specified time interval o Distribution of speeds over a specified time interval • Vehicle classification when more than one (1) sensor is deployed in a lane o Per-vehicle length o Report distribution of vehicle lengths over a specified time interval o The time interval for measurements shall be selectable from 30 seconds to 24 hours Each VSN shall transmit a unique identifying code. Each sensor in an installation shall be capable of being individually configured with its own sensitivity level. Sensitivity of the VSN shall be adjustable as may be required to detect bicycles and/or motorcycles. The VSN shall respond within 100 seconds when the AP or APCC/DR is powered on and transmitting. Two (2) types of sensor applications of sensors shall be available from the manufacturer. Type A shall provide all sensor functions, including data collection functions. Sensors used for this application shall provide for advanced system detection or stop bar detection. In the advanced system detection scenario a single Type A VSN shall be configurable to approximate the detection zones of 6-foot x 6-foot. In the stop bar detection scenario multiple Type A VSNs shall be configurable to emulate 6-foot x 6-foot to longer lengths. Type B sensors shall support presence detecti on only. Sensors used for this application shall provide for stop bar detection. In this scenario single or multiple Type B VSNs shall be configurable to emulate 6-foot x 6-foot to longer lengths. The plans shall dictate the sensor type required. The AP or APCC shall have the capability to transmit detection information to central software or a centralized server through several types of communication media, as required by the application. The AP shall be ca pable of communicating over a cellular data connection, or an Ethernet connection. The APCC shall be capable of simultaneously communicating detection data via the contact closure interface, Ethernet interface, and cellular data modem interface, as applicab le. The APCC cards shall provide sensor information processing and support the inte rface between a DR and the traffic controller using contact closure signals, or, for freeway applications, mounted in a stand-alone cabinet with direct IP communications. The AP or APCC shall have the capability to transmit detection information to 170, 2070, and NEMA TS1 and TS2 traffic controllers to provide real time detection information via a standard contact-closure based input shelf. The VSN, RP, DR, APCC or AP shall be capable of accepting software and firmware upgrades.
642.02.2 VSN Hardware. The VSN shall consist of a magnetometer, a microprocessor,
a wireless transmitter and receiver, battery, an “enclosure case”, and epoxy sealant for installation. The VSN components shall be contained within a single housing. The VSN housing shall meet NEMA 6P and IEC IP68 standards. The VSN components shall be fully encapsulated within the housing to prevent moisture from degrading the components. The VSN shall be able to operate at temper atures from -37°F to +176°F. The VSN shall be designed to operate from its battery for an average of 10 years of life under normal traffic conditions.
642.02.3 Repeater Hardware. The RP (if required) shall extend the effective
communication range of the sensor to the AP or DR an additional 750 feet. The RP communicating directly to an AP or APCC/DR shall support at least 10 sensors while an RP communicating to an AP or APCC/DR via an intermediate RP (i.e., tandem operation) shall support at least six (6) sensors. If the RP is battery powered, the RP battery shall be field replaceable. The RP shall operate in th e -37°F to +176° temperature range. All RP Components shall be contained within a single housing. The RP shall meet NEMA 4X and IEC IP67 standards. If battery powered, the RP shall be designed to operate from its battery for a minimum of seven (7) years of life under normal traffic conditions.
642.02.4 AP Hardware. The AP shall be the master device of the sensor network. The
AP shall be able to communicate to up to 48 VSN’s and 15 RP’s. The AP shall operate in the -37°F to +176°F temperat ure range. The AP shall meet NEMA 4X and IEC IP67 standards. It shall contain a weatherproof connector on the bottom of the device, which shall be shipped with a cover firmly attached to provide protection from the elements. The AP shall communicate via the following options: The controller via the Contact Closure Interface Card(s), Ethernet to a Central com puter/server, or simulta neously to both the controller and the Central computer/server.
642.02.5 Contact Closure In terface Card (CCI) and Expa nsion Card System (EX)
Hardware. The Contact Closure Cards and Expansion Cards, collectively called Contact Closure Interface Card(s) (CCI), shall provide detector outputs to the controller. The CCI shall directly plug in to the standard 170/2070 Input Files and NEMA detector racks and detection file type shall be selectable via dipswitch. Each CCI card shall provide up to four
4.channels of detection. Additional contact closure input channels shall be provided via Expansion Cards (EX) daisy chained to the CCI (user configurable from one (1) to four (4) outputs each). All required EX cards to handle the number of sensors or controller channels as indicated in the plans or project specifications shall make up the Expansion Card System. The CCI shall be able to provide pulse or presence detection outputs. The front panel of the CCI shall provide: • Status LED’s displaying o Detection Channel Status o Line Quality o Fault Monitor The CCI shall be powered by 11 to 26 VDC. The CCI shall be surge protected to GR-1089 standards. The CCI card(s) shall operate -37°F to +176° temperature range. The CCI shall operate in up to 95% humidity (non-condensing).
642.02.6 Access Box. The access box shall provide a communication link between the
AP and CCI card(s). The access box shall provide the ability for remote communications.
642.02.7 Access Point Contact Closure (APCC) Interface Card and Expansion Card
System (EX) Hardware. The APCC shall also serve as the master device of the MDS, where AP type configurations are not specif ied. It shall provide all the higher level processing and interface functions of the MDS system and shall only require a single detection rack width slot. All required EX cards to handle the number of sensors or controller channels as indicated in the plans or project specifications shall make up the Expansion Card system. Each APCC card shall provide detector data as contact closure signals to the traffic controller. The APCC card shall be capable of plugging directly in to standard 170/2070 input files and NEMA detector racks or shall be supplied within a standard enclosure to supply power for use in freeway applications. The APCC and EX cards front panel shall be configurable either via software or via front panel switches to provide presence/pulse mode, delay timing and extension timing. The front panel of the APCC and EX card system shall provide LED’s to monitor: • Detection Channel Status • Line Quality • Fault Monitor APCC and EX card system shall operate at temperatures from -37°F to +176°F, and in humidity up to 95% (non-condensing).
642.02.8 Digital Radio Hardware. The Serial Port Protocol Digital Radio (DR) shall
support at least 48 sensors with a 0.125 second latency. It shall contain a weatherproof connector on the bottom of the device, which shall be shipped with a cover firmly attached to provide protection from the elements. The DR shall operate at temperatures from -37°F to +176°F, and DR shall be contained within a single housing that conforms to NEMA Type 4X and IEC IP67 standards.
642.02.9 Isolator (ISO) Module. If required, an Isolator Module may be used in between
each DR and APCC to extend communications range and protect the APCC card from transient surges. The Isolator Module shall extend the communication range between the APCC and DR from 30 feet to 2000 feet. The Isolator Module shall provide electrical isolation of 1500V, surge protection of up to 1500V, and shall provide AC power cross protection.
642.02.10 Input/Output (I/O) Module. The MDS may include I/O modules to expand
the capabilities of an APCC by providing additional communication options, memory options and a battery backed real time clock. The module shall include a RS232 port for serial communications. As an option, it may also allow for detection data shall be communicated as IP data over either GSM-based cellular data services via a GPRS cellular modem or over CDMA based cellular data services via a 1xRTT cellular modem.
642.02.11 Configuration Software. The MDS shall include the software necessary to
configure the VSN. The MDS shall include the software necessary to configure the RP, AP, APCC, EX, CCI and DR.
642.02.12 Epoxy. The MDS shall also include the necessary epoxy for installation. The
epoxy used for installation of the sensor(s) shall be a two part poly-urea based joint sealant having self-leveling characteristics. Surfaces the epoxy will be bonding to shall be free of debris, moisture, and anything else which might interfere with the bonding process. The epoxy used shall be approved by the manufacturer of the detection system.
642.03 Construction Requirements.
642.03.1 Installation. The flush mount sensors shall be installed in the roadway using
the following procedure. The roadway shall be core drilled to provide a hole, 2.5 inches deep. The hole shall be cleaned out per the manufactures recommendation and leveled prior to placement so that the sensors will remain flush once installed. A small layer of epoxy to cover the bottom of the hole shall be applied. The sensor shall then be placed on top of this layer of epoxy in the correct orientation. The sensor shall be fully encapsulated with the epoxy to the lip of the cored hole. The AP or DR and RP shall be installed within range of the sensors as specified by the manufacturer. Once the installation is complete, the Contractor shall provide documentation to the Engineer that includes an intersection diagram of sensor IDs and their placement.
642.03.2 Removal. The direction of traffic flow shall be permanently marked on top of
the sensor prior to removal. The sensor and its epoxy coating shall be removed from the roadway by coring a hole to a depth of 2.50 inches with the sensor and epoxy being contained in the center of the core. The core shall then be extracted from the roadway using a pry bar as needed and retained for reinstallation upon completion of roadwork.
642.03.3 Reinstallation. Cores containing previously removed sensors shall be
reinstalled by coring a 5-inch hole in the roadway to a depth of 2.5 inches. The core shall be placed inside the hole in the correct orientation. The sensor shall be fully encapsulated with the epoxy to the lip of the cored hole. The sensors shall be configured as needed to provide vehicle detection and operate with existing system AP or APCC, DRs, and RP’s, as well as existing cabinet components.
642.03.4 Limited Warranty. The supplier shall provide a limited 5-year warranty on the
detection system from the point of the project final acceptance. During the warranty period, technical support shall be available from the supplier via telephone within 24 hours of the time a call is made by a user, and this support shall be available from factory- authorized personnel or factory-authorized installers. During the warranty period, standard updates to the software shall be available from the supplier without charge.
642.03.5 Testing and Accuracy Requirements. At the Engineer’s request, the
Contractor or Supplier shall provide a Wireless Magnetometer Vehicle Detection System that meets the below minimum accuracy requirements for all conditions. Accuracy measurements for the testing shall be done with an appropriate sample size of vehicles, over a specific time period. At the Engineer’s request, the Contractor shall submit to the Engineer the Test Plan for Accuracy testing at the location(s) that is site specific to the plans. The test plan shall take into account the roadway type (freeway, arterial), location (urban, rural), and traffic conditions in order to determine appropriate testing length and sample size. The following conditions shall be met for each sensor installed:
1.Measurement Accuracy The following error levels shall be achievable and demonstrated during testing. Parameter Error Percentage Presence ......................................... ±2% Lane Occupancy ............................ ±5% Volume .......................................... ±8% Average Speed .............................. ±10% Length Classification limits .......... ±10%
2.Testing At the Engineer’s request, plans shall be developed and submitted to the Project Engineer for consideration and approval for post-installation testing. The plans test shall include all functional requirements and the accuracy requirements. The testing shall prove that all in-pavement sensors are configured appropriately. The following post installation test procedures shall be utilized after the MDS is installed in its entirety as shown in the plans and is integrated with the existing traffic signal control central software. No post-installation testing shall begin until all MDS systems in the project have been configured/calibrated to gather speed, volume, classification, and occupancy, or presence, as dictated by the application and programmed to communicate on the Department’s ITS network. Including the accuracy testing requirement, at a minimum, provide the following on the test plan to be submitted and approved by the Engineer:
a.Inspect all detection system field components to ensure proper installation and cable termination.
b.Verify that field construction has been completed as specified in the plans.
c.Inspect the quality and tightness of ground and surge protector connections.
d.Check power supply voltage and outputs and ensure device connections are as specified in the plans.
e.Verify that the installation of cables and connections between all AP’s to CCI cards, and DR’s to APCC’s are per manufacturer recommendations and as specified in the plans
f.Demonstrate that each Wireless In-Pavement Vehicle Detection System is fully operational and gathering the required data types at the specified interval to the central software or controller, as required by the application.
642.03.6 Maintenance and Support. The supplier shall maintain a sufficient inventory
of parts to provide support and maintenance of the system. These parts shall be available for delivery within 30 days of receipt of a purchase order by the supplier at the supplier’s then current pricing and terms of sale. The supplier shall maintain an ongoing program for customer support for the system. This support shall be via telephone, email or personnel sent to the installation upon receipt of an purchase order at the suppliers then current pricing and terms of sale for technical support services. Installation and/or training support shall be provided by a factory authorized representative. All documentation shall be provided in the English language.
642.04 Method of Measurement. Magnetometer Detection System will be measured as
a unit per each for system installation. Magnetometer Detection System Component of the type specified will be measured as a unit per each. Magnetometer Detection System Component Removal and Reinstallation will be measured as a unit per each.
642.05 Basis of Payment. Magnetometer Detection System, measured as prescribed
above, will be paid for at the contract unit price per each, which price shall be full compensation for furnishing all materials, controller modifications, connectors, wiring, software, epoxy sealant, testing, equipment, labor, tools, and all incidentals necessary to complete the work. Magnetometer Detection System and Magnetometer Detection System Components, measured as prescribed above, will be paid for at the contract unit price per each, which price shall be full compensation for all materials, connectors, modifications, hardware, connectors, wiring, cabling, mounting brackets, testing, equipment, labor, tools, and all incidentals necessary to complete the work. Magnetometer Detection System Component Removal and Reinstallation, measured as prescribed above, will be paid for at the contract unit price per each, which price shall be full compensation for all work necessary to completely remove and reinstall an existing component, any necessary epoxy sealant, controller modifications, connectors, wiring, software programming, and all incidentals necessary to satisfactorily remove and reinstall an existing component. Payment will be made under: 642-A: Magnetometer Detection System - per each 642-B: Magnetometer Detection System Component, ________ - per each 642-C: Magnetometer Detection System Component Removal and Reinstallation, ________ - per each
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Source: Standard Specifications for Road and Bridge Construction, 2017 Edition. Pages 609–615 of 1,113. View official source ↗