IMSA Traffic Signal II flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Warrant 1

The MUTCD Eight-Hour Vehicular Volume warrant, satisfied when traffic volumes on both the major and minor approaches exceed the specified thresholds for eight hours of an average day.

Warrant 3

The MUTCD Peak Hour Vehicular Volume warrant, met when both the minor-street volume and the major-street approach volume exceed their limits during any single hour.

Overhead signal head clearance

The bottom of a signal housing and its attachments installed over a roadway must be at least 15 feet above the pavement to clear vehicles.

One primary signal per through lane

MUTCD requires a primary signal face for each through lane, located over or as close as practicable to that lane so drivers can see their assigned indication.

Mast arm wind load design

Poles, mast arms, and span wires are sized for wind load using AASHTO LTS with the signal, sign, and luminaire loads given on the design plans.

Verify plan bar scale

Dimensions must be checked against the printed bar scale, because scaling from a reduced, re-plotted, or scanned sheet produces inaccurate measurements and layout errors.

NEC conduit fill limit

NEC Chapter 9 permits no more than 40 percent fill in a raceway containing three or more conductors, and it also sets minimum bend radius and pull-point rules.

Anchor bolt torque

After the pole is plumbed on its leveling nuts, the anchor bolt nuts are tightened to the torque value specified by the pole manufacturer before grouting.

Equipment grounding conductor

The insulated conductor that bonds each metal pole, cabinet, and device to the service ground, as required by NEC Article 250 for fault current return.

Trench protective system

OSHA 29 CFR 1926 Subpart P requires sloping, shoring, or a trench box for excavations 5 feet deep or more to protect workers from cave-in.

Loop lead-in twisting

Lead-in cable from a detector loop is twisted about four to six turns per foot so induced noise from nearby power conductors cancels and does not cause false calls.

Cable pulling lubricant

Lubricant reduces friction during installation; exceeding the cable's maximum pull tension or minimum bend radius will stretch or damage the conductors and jacket.

Foundation cure before erection

Poles are not set until the concrete foundation reaches its specified cure period or strength, commonly seven days or 75 percent of design compressive strength.

Yellow change interval formula

Y equals perception-reaction time plus V divided by (2a + 64.4g), where V is approach speed in mph, a is deceleration in ft/s², and g is grade.

Red clearance interval formula

R equals (W + L) divided by V, where W is the distance from the stop line to the far side of the conflicting area and V is speed in feet per second.

Passage time

The vehicle extension interval, typically 2.0 to 3.0 seconds, that holds a phase green after a detector actuation while the vehicle travels to the stop line.

Minimum recall

A controller setting that places a call for a phase every cycle so the phase is always served, even when no detector actuation occurs.

Coordination offset

The time shift applied to a coordinated controller's cycle relative to system time zero, used so platoons of vehicles arrive during the green interval.

Conflict monitor (MMU)

A device that monitors field outputs for conflicting greens, absence of red, and improper voltage, and forces the intersection to flashing operation when a fault occurs.

NEMA TS-2 controller

A controller standard using A, B, and C harness connectors and SDLC serial links to detectors and the monitor, replacing the parallel wiring of TS-1.

Protected-permissive left turn

Left-turn operation in which the movement runs protected on a green arrow and permissive during the opposing through green, shown by a flashing yellow arrow.

Conflict monitor fault log

The stored fault code shown on the monitor after a trip; it must be recorded before reset, because resetting clears the diagnostic history.

Loop inductance baseline

A healthy detector loop reads roughly 100 to 800 microhenries; a large deviation from the recorded installation value indicates an open or shorted loop.

Phantom LED glow

Faint illumination of an LED indication caused by leakage current in the field wiring, cured by repairing the leakage path or adding a bleeder resistor.

No-green troubleshooting order

Check detector actuation first, then call registration at the controller, then recall and coordination settings, and finally field wiring and the LED or lamp module.

Cabinet preventive maintenance

Scheduled cabinet service includes replacing fan filters, renewing desiccant, checking surge arrestors, verifying battery voltage, and torquing terminal connections.

Ground fault isolation

Disconnect field circuits and megger each conductor to ground; a sharp drop from the installation baseline resistance points to moisture intrusion or damaged insulation.

Taper length formula

L equals W times S for speeds of 40 mph or less, and L equals W times S squared divided by 60 for 45 mph or more, with W in feet.

Buffer space

The unoccupied area in a temporary traffic control zone between the work space and the traffic space that provides recovery distance for errant vehicles.

High-visibility apparel

ANSI/ISEA 107 Class 2 or Class 3 garments are required for workers exposed to traffic while operating within the highway right-of-way.

Flagger STOP/SLOW paddle

The standard retroreflective hand-signaling device used by flaggers to stop and release traffic, used with a clear sight line to approaching drivers.

Activity area

The portion of a temporary traffic control zone where work occurs, containing the work space, the buffer space, and the traffic space.