Inputs
Example data table
| Cycle (s) | Intersections | Segment distances (km) | Segment speeds (km/h) | Green starts (s) | Green durations (s) |
|---|---|---|---|---|---|
| 90 | 3 | 0.35, 0.40 | 35, 35 | 5, 25, 45 | 30, 30, 30 |
| 120 | 4 | 0.30, 0.25, 0.35 | 30, 28, 32 | 10, 40, 70, 95 | 35, 30, 30, 25 |
These sample values illustrate how corridor travel affects arrival alignment at each downstream intersection.
Formula used
- Segment travel time: t = (D / V) × 3600, where D is distance (km) and V is speed (km/h).
- Cumulative travel time: sum of segment travel times from Intersection 1 to k.
- Arrival time (mod cycle): A = (G1 + Tcum) mod C.
- Arrives on green: arrival falls inside the green window, including wrap-around.
- Recommended offset vs 1: O = (Gk − (G1 + Tcum)) mod C.
- Progression score: 100% when arrival is on green; otherwise reduced by the estimated wait and platoon spread.
How to use this calculator
- Set a common cycle length for the corridor.
- Choose how many intersections you want to coordinate.
- For each intersection, enter the green start and green duration.
- For each segment, enter distance and expected travel speed.
- Click Calculate Coordination to see arrivals, waits, and offsets.
- Download CSV or PDF from the summary card for reporting.
Article
1) Why coordination matters in construction corridors
Temporary lane shifts, flagging, and short storage lengths create unstable queues. Coordinated signals reduce repeated stopping, limit rear‑end risk, and keep heavy vehicles moving predictably through the work zone. Even modest improvements in progression can cut field complaints and reduce lost time for deliveries and crews.
2) Key timing data you should collect on site
Start with a common cycle length that matches the dominant demand period. Record each intersection’s green start and green duration for the coordinated movement. Measure segment distance and realistic travel speed, not posted speed. If trucks climb grades or pass narrow shifts, speeds commonly drop 10–30%.
3) How the calculator evaluates arrivals and delays
The calculator converts distance and speed into seconds of travel time, then adds cumulative travel to the upstream release time. Arrival is evaluated within the same cycle using a modulo operation. If arrival misses the green window, the tool estimates how long until the next green begins.
4) Using offsets to improve progression
Offsets represent how downstream green starts should align with expected platoon arrivals. When the recommended offset differs from current timing, adjust green start values or the cycle. In practice, keep offsets stable during peak periods, then recheck after traffic control changes or when haul routes shift.
5) Interpreting the progression score for decisions
The progression score summarizes how well arrivals align with greens, penalizing long waits and oversized platoon windows. Use the average score to compare alternatives: different cycle lengths, revised green durations, or updated speeds. A higher score typically means smoother travel, fewer stops, and lower queue growth.
FAQs
1) What does “cycle length” mean?
The cycle length is the total time for a complete signal sequence to repeat. Coordination assumes all intersections share the same cycle so arrivals can be compared consistently across the corridor.
2) Can I coordinate intersections with different cycles?
True coordination requires a common cycle. If field controllers differ, choose a feasible shared cycle or use a common multiple. Otherwise, arrivals drift and progression deteriorates quickly.
3) How should I pick travel speed for segments?
Use observed work‑zone speed during the period you want to coordinate. Include delays from merges, narrow lanes, or grade effects. Overstating speed makes predicted arrivals early and reduces accuracy.
4) What is the recommended offset vs Intersection 1?
It is the suggested shift for each downstream green start so that a platoon released at Intersection 1 reaches that intersection during its green window, within the chosen cycle.
5) Why does the score drop when platoon window is large?
A wide platoon window means vehicles arrive spread out. If the green duration is shorter than that window, some vehicles will miss green and wait, so the score is reduced.
6) Does the tool include yellow and all‑red intervals?
The inputs focus on the coordinated green window. If you need to be conservative, reduce the green duration by clearance time so arrivals are judged against the effective green.
7) When should I recalibrate coordination?
Recalibrate after traffic control changes, major volume shifts, or speed changes from new detours. For active sites, a quick weekly check during peak demand keeps timing realistic.