ITS ADVENTURES & FIELD MYSTERIES
When an ITS cabinet mysteriously loses communication, this underground component is often the first suspect on the “crime scene.
What is a fiber splice (or fiber break)?
Every signal designer’s favorite phrase — this sheet shows the exact location of poles, cabinets, and signal heads.
What is the signal layout sheet?
When a signal stays green a little longer because cars are still arriving, this timing magic is at work.
What is gap‑out?
This federal manual helps engineers predict crashes using statistical models — essential for HSIP projects.
What is the Highway Safety Manual?
This analysis predicts how much new traffic a development will generate — often becoming Exhibit A in community meetings.
What is a TIA (traffic impact analysis)?
This ITS device is the traffic engineer’s “eye in the sky,” watching for congestion, incidents, and the occasional rogue road‑crossing animal
What is a CCTV camera?
This intersection type removes left turns at the main intersection and sends them to downstream U‑turns — confusing drivers, but improving safety.
What is a MUT (median U‑turn)?
This measure tells engineers just how painful a driver’s experience was at an intersection — the higher it is, the louder the complaints.
What is control delay?
If you want to know WHY crashes are happening, you create this — often revealing patterns like rear‑ends or angle collisions.
What is a collision diagram or crash pattern analysis?
When planning future improvements, engineers use this metric — a measure of how much demand exceeds capacity.
What is the v/c ratio?
These roadside units allow cars to “talk” to traffic signals, a foundational step toward connected vehicle ecosystems.
What are RSUs?
This type of phase gives left‑turning drivers their own exclusive green, helpful at crash‑heavy intersections but dreaded by coordinators.
What is protected‑only left‑turn phasing?
This tool simulates traffic like a video game, showing engineers how platoons, queues, and chaos unfold in real time.
What is VISSIM?
This countermeasure flashes so brightly that drivers usually stop — and occasionally stop way too early.
What is an RRFB?
This level‑of‑service grade represents total gridlock and pure despair — but still appears in real planning studies.
What is LOS F?
Engineers sometimes find mysterious extra cables in old cabinets; they likely belonged to this outdated but once‑popular communication technology.
What is twisted‑pair copper?
A signal head must never be placed behind this — unless the goal is immediate driver confusion and multiple angry calls to 311.
What is an obstruction (tree, sign, or utility pole)?
Engineers often adjust offsets to give drivers (and themselves) this magical experience of hitting green after green.
What is progression?
This safety method adjusts crash predictions based on real‑world observations, producing more accurate “after” results.
What is the Empirical Bayes method?
This transport trend focuses on compact, mixed‑use development near transit stations — a favorite of planners but a challenge for engineers.
What is transit‑oriented development (TOD)?
A traffic engineer knows a corridor is cursed when this network structure is missing — meaning ONE fiber cut takes down EVERYTHING.
What is a ring topology?
When designing high‑volume arterials, engineers love adding these lanes — because nothing reduces delay like giving turning drivers their own space.
What are auxiliary/turn lanes?
This timing parameter is the backbone of coordination — too short and platoons break; too long and everyone hates you.
What is the cycle length?
If an intersection shows high pedestrian crash exposure, engineers calculate this ratio to determine whether improvements are needed.
What is the crash rate?
Long‑range transportation plans rely heavily on these multi‑decade population and employment forecasts from MPOs.
What are regional demographic projections?