IMSA Traffic Signal II cheat sheet

MUTCD Chapter 4C contains nine signal warrants; a signal is justified only when at least one warrant is satisfied by an engineering study (Warrant 1 = Eight-Hour, 2 = Four-Hour, 3 = Peak Hour).

A primary signal face is required for each through lane, mounted over or as close as practicable to that lane; supplemental faces may be added over the same lane.

The bottom of a signal housing over a roadway must be at least 15 ft above the pavement; post- or pedestal-mounted faces are set at the clearance shown on the standard plan.

Mast arms, span wires, and poles are structurally designed for wind load per AASHTO LTS using the signal, sign, and luminaire loads listed on the plan sheets.

Layout sheets follow standard scales such as 1 in = 20 ft or 1 in = 10 ft; verify all dimensions against the printed bar scale before scaling.

NEC Chapter 9 limits conduit fill to 40% for three or more conductors, and sets minimum bend radius and pull-point requirements.

Pull boxes or handholes are typically placed at each pole, at each change of direction, and at intervals not exceeding about 150 ft.

Plan symbols establish pole numbers, controller location, detector loops, conduit runs, service point, and utility conflicts; the legend governs interpretation.

Detector loops are laid out per lane with the loop dimensions and number of turns shown in the loop schedule, with lead-in routed to the nearest handhole.

Poles are not erected until the foundation reaches the specified cure period or compressive strength, commonly 7 days or 75% of design strength.

Anchor bolt nuts are torqued to the pole manufacturer's value after the pole is plumbed on leveling nuts; grout is placed after alignment is verified.

NEC Article 250 requires each metal pole, cabinet, and device to be bonded to the equipment grounding conductor and to a ground electrode.

Neutral and equipment grounding conductors are kept separate in the cabinet and bonded only at the service point.

Cable pulling requires lubricant, respect for the cable's minimum bend radius and maximum pull tension, and about 3 ft of slack at each handhole.

OSHA 29 CFR 1926 Subpart P requires sloping, shoring, or a trench box for excavations 5 ft deep or more.

Loop lead-in cable is twisted, typically 4 to 6 twists per foot, to cancel noise induced from adjacent power conductors.

A megohmmeter insulation-resistance test and a point-to-point continuity check are performed before energizing; typical new-cable acceptance is 50 MΩ or more at 500 V DC.

Yellow change interval: Y = t + V / (2a + 64.4g), where t is perception-reaction (about 1.0 s), V is approach speed in mph, a is deceleration in ft/s², and g is grade in ft/ft (positive uphill).

Red clearance interval: R = (W + L) / V, where W is the distance from the stop line to the far edge of the conflicting area, L is vehicle length, and V is speed in ft/s.

Minimum green must clear the detector-to-stop-line queue or satisfy pedestrian WALK plus clearance time, whichever governs.

Passage (vehicle extension) time is typically 2.0 to 3.0 s; gap reduction lowers the extension value the longer a detector remains occupied.

Coordinated-actuated operation is defined by cycle length, offset, split, and force-off points.

Recall modes: minimum recall places a call every cycle; maximum recall also holds the phase to maximum green; pedestrian recall places a pedestrian call every cycle.

NEMA TS-1/TS-2 controllers use A, B, and C harness connectors and SDLC serial links to detectors and the MMU; Type 170 and 2070 controllers use backplane bus architecture.

The conflict monitor (MMU) checks field outputs for conflicting greens, absence of red, and improper voltage, and forces the cabinet to flashing operation on a fault.

Protected-permissive left turns run protected on the arrow and permissive during the opposing through green, displayed with a flashing yellow arrow or doghouse.

After a conflict monitor trip, record the displayed fault code from the MMU before pressing reset, because resetting clears the diagnostic evidence.

No-green diagnosis sequence: confirm detector actuation, verify call registration at the controller, check recall and coordination settings, then inspect field wiring and the LED/lamps.

Healthy loop inductance is roughly 100 to 800 microhenries; a large deviation from the recorded baseline indicates an open or shorted loop or lead-in.

Faint 'phantom' illumination of an LED indication comes from leakage current in the field wiring; a bleeder resistor across the field terminal or wiring repair eliminates it.

Cabinet preventive maintenance: replace fan filters, renew desiccant, check surge arrestors, verify battery voltage, and torque terminal connections.

Loop failures commonly trace to saw-cut sealant failure, pavement cracking, or lead-in cable damage at the handhole splice.

Ground faults are isolated by disconnecting field circuits and meggering each conductor to ground; a sharp drop from the installation baseline indicates moisture or damaged insulation.

Taper length: L = W × S for speeds of 40 mph or less, and L = W × S² / 60 for 45 mph or more, where W is width in feet and S is speed in mph.

A temporary traffic control zone consists of the advance warning area, transition area, activity area, and termination area.

The activity area contains the work space, buffer space, and traffic space; buffer space is unoccupied and provides recovery distance for errant vehicles.

Flaggers use a retroreflective STOP/SLOW paddle; AFADs are used only where permitted by MUTCD and agency policy.

Workers exposed to traffic within the right-of-way wear ANSI/ISEA 107 Class 2 or Class 3 high-visibility apparel.

MUTCD Part 6 governs temporary traffic control; Part 4 governs traffic signals, including temporary signals used in TTC zones.

Drums used for channelization are at least 36 in tall; cones must meet the height specified for the posted speed.

Temporary signals in work zones need a backup power source or a flagger contingency plan if a failure could create conflicting movements.