704.01 Description. This item shall consist of furnishing and
installing vehicle detectors and/or rack mounted ve hicle detectors, loop wiring and/or preformed detector loops, and ne cessary feeder wire according to these specifications and at the l ocations shown on the plans or as directed.
704.02 Materials. (a) General. Each loop detector shall be
composed of all components necessary to provide for the detection of vehicles constituting one traffic phase and shal l include an electrical surge protection device. Each vehicle detector shall be supplied complete wi th comprehensive instructions. The instructions shall be placed in the controller cabinet. The term "vehicle detector" as used in these specif ications shall refer to the pulse amplifying unit located in the c ontroller cabinet. The term "loop wiring" as used in these specificati ons shall refer to the sensing element and single conductor wire fr om the sensing element to the feeder wire. The wire shall be 14 g age stranded copper wire and shall be insulated with RHH or RHW USE rated insulation not less than 0.045" (1.1 mm) thick. The term "feeder wire" as used in these specificati ons shall refer to the shielded 1, 2, or 4 pair 14 gage stranded co pper wire extending from the detector unit to the loop wiring at the curb or pavement edge. The wire in each pair shall be twis ted and each pair shall be shielded. Each loop shall have a separate feeder wire unless noted otherwise on the plans. All vehicle detectors at a given intersection shall be housed inside the controller cabinet for that intersection. The Contractor shall submit to the Engineer for app roval two copies of the applicable brochures containing desig n criteria for the components. The specific items proposed for use s hall be clearly marked in the brochures. If more than one item is submitted at one time for Department review, a list shall be attache d showing each item for which Department approval of design charac teristics is being requested. The Engineer will provide written approval of the design characteristics.
b.Vehicle Detector Requirements. Vehicle detectors shall: • be designed to operate satisfactorily in temperatur es ranging from -30° F to +140° F (-34° C to +60° C), • be designed to operate satisfactorily on line volta ge ranging from 100 to 130 VAC, • operate on 115 VAC, 60 Hz power, • be so designed that the detector, operating in the pulse mode, will ignore a vehicle parked over a loop or portion thereof in 30 to 180 seconds. After ignori ng the parked vehicle, the remainder of that loop shall de tect additional vehicles, • be capable of giving detection signals persisting f or up to 5 minutes if a vehicle stops and remains over th e loop when operating in the presence mode, • be capable of detecting vehicles ranging in size fr om a motorcycle to a large tractor trailer, • be designed to run feeder wire in common conduit wi th signal and interconnect cable without interference, and • be capable of driving 1 or 2 loops over a feeder le ngth totaling up to 600 feet (180 m). • be equipped with optical coupled or relay output ci rcuts. • be equipped with transformer isolation for loops. • be equipped with high intensity LED indicators. • be equipped with continuous loop monitor • be equipped with time delay (where specified in the plans) “With Count” specified detectors shall meet the abo ve requirements and the “Count Output” function shall provide a separate pulse for each vehicle entering the loop d etection zone to a separate controller input (in addition to the stand ard detector output).
c.Electrical and Mechanical Requirements. The vehicle detector unit shall be: • plug connected to controller terminal facilities, • completely self contained, self tuning, and shall not require external power supplies other than line vol tage, and • of a design suitable for shelf mounting inside the controller cabinet.
d.Preformed Detector Loops. This item shall be constructed utilizing an approved preformed loop listed on the Department’s Qualified Products List. The preformed detector loop shall be constructed of #20 AWG (minimum) stranded copper wire, encapsulated in a f lexible sealant inside a reinforced 250 psi (1724 kPa) rubber hose or approved tubing. No wire splices will be allowed in the loo p assembly. Hose for the loop and lead-in shall be one continuous pi ece except for the required tee connectors. Encapsulated wire shall h ave two (2) turns for loops with a perimeter greater than 40 ′ (12 m); or three (3) turns for perimeter less than or equal to 40 ′ (12 m). Quadrupole loops shall be two turn (2-4-2) configuration.
e.Rack Mounted Vehicle Loop Detectors. Rack mounted vehicle detectors shall consist of the following pr incipal components: two (2) or four (4) channel vehicle de tector (card rack type); power supply unit (card rack type); and card rack (for plug-in modules). The components shall have the features s hown below.
1.Vehicle Detectors – Rack Mount. The single module will operate the detectors from a 24 VDC supply. E ach detector shall meet the requirements of (b) above and the fo llowing: • Connectors shall consist of double sided edge card connectors. • “With Count” detectors shall provide two standard detector outputs and two count outputs to insert in to a four channel rack position.
2.Power Supply Unit. The power supply unit shall be a card rack type with an input voltage of 90 – 135 VA C, 60 Hz. Output voltage shall be unregulated DC. The unit s hall contain high intensity LED indicators and one power switch that switches input line voltage for all channels. The unit modu le shall be fully compatible with the rack mounted vehicle detectors and other associated equipment.
3.Card Rack. The vehicle detector card rack shall be constructed of lightweight anodized aluminum with m ounting flanges to allow mounting of the rack either above or below the controller cabinet shelf. Each rack shall accommod ate a minimum of two – 4 channel power supply units and u p to eight – 2 channel detector units. Each rack shall be abl e to hold a maximum module size of 4.5 ″ x 6.875 ″ (115 mm x 175 mm). The connector wire shall be #22 AWG-Type UL 1015-10 50C. The rack unit shall be fully compatible with the di gital loop detectors and other associated equipment.
704.03 Construction Requirements. (a) General. The vehicle
detectors, loop wiring, and feeder wire shall be in stalled as shown on the plans or as directed by the Engineer. The l oop wiring shall be installed in a sawed slot 1/4" to 3/8" (6 mm to 10 mm) wide, 2½" (65 mm) minimum depth in asphalt or 1½" (40 mm) in concrete, or as indicated on the plans. In no case shall the wi re be less than 1¼" (32 mm) below the final pavement surface. Before s ealing the slot, the wire shall be held down by backer rod wedges in serted into the slot at a maximum of 2' (0.6 m) intervals. Loop wiring shall be tested by the Contractor accor ding to the procedures outlined on the plans. There shall be no splices in the feeder wire or the loop wiring. The backer rod and sealant used shall be listed on the QPL. The installation procedures shall be according to the m anufacturer's recommendations.
b.Preformed Detector Loops. Preformed Detector Loop shall be designated by the perimeter size and configurati on. The Contractor shall be responsible for determining the length of lead-in from loop to connection with feeder wire. Lead-in from feeder wire to the loop shall be considered incidental to the P reformed Detector Loop. The preformed loop shall be placed in a saw-cut slo t of sufficient width (approximately ½ ″ [6 mm] to ¾″ [19 mm] in width) to a depth such that the top of loop is a minimum of 4 ″ (100 mm) below the final surface, for the entire length of the trench. The maximum width of any loop trench shall be 1½ ″ (38 mm). The minimum width shall be 1/8 ″ (3 mm) larger than the outer diameter of the preformed loop. Larger widths shall be used for co uplings, tees, and ells but not to exceed the maximum width. The corn ers of the trench should be chiseled to remove the sharp edge. The Engineer may approve other methods of trenching. Where the road surface is to be overlaid, the prefo rmed detector loops shall be installed prior to final surface. T he Contractor shall seal and compact the loop trench completely with a material and/or sealant recommended by the loop manufacturer. The recommended material shall be able to repair asphalt and concre te roads and not require removal and/or replacement if the pavement is to be overlaid. Where surface is not to be overlaid, an approved sealer shall be applied to backfill the preformed loop tre nches as needed to a minimum depth of 3/8 ″ (10 mm). The approved material shall have a minimum settlement period of 14 days prior t o each backfill application. The connection of the loop lead-in to the feeder wi re shall be soldered and completely sealed in an approved manne r against entry of moisture into the splice, jacket of loop and fee der wire. The preformed detector loop shall be tested for meg and continuity according to the procedures outlined on the plans a nd each feeder wire shall be clearly labeled with the phase design ation.
c.Rack Mounted Vehicle Detectors. Wiring diagrams for the vehicle detector channel assignment shall be provid ed to the Department for approval prior to the delivery of th e controller cabinet to the Contractor. The vehicle detector card rack’s mounting flanges s hall be turned out on each rack and the power supply modules shall be located on the left side when viewed from the front. All output channels available from the card rack, i ncluding unused channels, shall be brought out to the termin al strips for future use. This shall include providing terminals for future detector loops. Where unused system detector inputs to the controller are available, these shall be tied to unused detector c hannels or brought out to the terminal facilities. If approved by the Engineer, 2-channel units may be used in combination with 4-channel units in order to reduce the number of unused channels. This may be allowed provided that the possibility of cross talk will not be increased.
704.04 Method of Measurement. Items will be measured as
follows:
a.Vehicle Detectors will be measured by the unit.
b.Loop Wiring will be measured by the linear foot (me ter).
c.Feeder Wire will be measured by the linear foot (m eter).
d.Preformed Detector Loops will be measured by the un it for the size, type, and number of turns specified. Siz e shall be designated by length and width dimensions. Type sh all be Q for quadrupole configuration (2-4-2) and blank for stan dard configuration.
e.Vehicle Detector - Rack Mount will be measured by the unit for the number of standard vehicle detector channel s provided.
f.Vehicle Detector - Rack Mount, with Count will be measured by the unit for the number of standard vehicle dete ctor channels provided (including one separate count output chann el). No separate payment will be made for count output chan nels.
g.Vehicle Detector - with Count will be measured by the unit for the number of standard vehicle detector channel s provided (including one separate count output channel). No separate payment will be made for count output channels.
704.05 Basis of Payment. Work completed and accepted and
measured as provided above will be paid for as foll ows:
a.Vehicle Detectors will be paid for at the contract unit price bid per each for Vehicle Detector, or Vehicle Detec tor-with Count, which price shall be full compensation for furnishi ng, mounting, and installing the detector; and for all materials, lab or, equipment, tools, and incidentals necessary to complete the work.
b.Loop Wiring will be paid for at the contract unit p rice bid per linear foot (meter) for Loop Wiring, which price sh all be full compensation for laying the loop wiring in place an d connecting to the appropriate feeder wire; for sawing and sealing as appropriate; and for all materials, labor, equipment, tools, and incidentals necessary to complete the work.
c.Feeder Wire will be paid for at the contract unit p rice bid per linear foot (meter) for Feeder Wire, which price sh all be full compensation for laying the feeder wire in place an d connecting to the appropriate vehicle detector and loop wiring; f or pulling wire through conduit; and for all materials, labor, equi pment, tools, and incidentals necessary to complete the work.
d.Preformed Detector Loops will be paid for at the c ontract unit price bid per each for Preformed Detector Loop (__ ′ x __ ′) (__ m x __m), which price shall be full compensation for sa wing and sealing; clearing the slot; removal of surplus mate rial; placing the preformed detector loop in place and connecting to the appropriate feeder wire; and for all materials including the pr eformed loop, asphalt or sealer material, coupling and connectors ; and for all labor, equipment, tools, and incidentals necessary to comp lete the work.
e.Rack Mounted Vehicle Detectors will be paid for at the contract unit price bid per each channel for Vehicl e Detectors-Rack Mount or Vehicle Detectors-Rack Mount, with Count, which price shall be full compensation for furnishing and insta lling the detector card rack, power supply, detector cards, and for al l equipment, tools, labor, and incidentals required to complete the wor k. Payment will be made under: Pay Item Pay Unit Vehicle Detector Each Vehicle Detector-with Count Each Loop Wiring Linear Foot (Meter) Feeder Wire Linear Foot (Meter) Preformed Detector Loop (__ ′ x __ ′) (__ m x __m) Each Vehicle Detector-Rack Mount Each Vehicle Detector-Rack Mount, with Count Each
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