Intersection Delay Calculator

Enter shared signal settings, then define up to four approaches. Leave unused approach rows blank.

Method HCM-style (uniform + incremental) Webster-style (undersaturated)

Pick HCM-style for general use; Webster works best when v/c < 1.

Cycle length C (seconds)

Typical urban range: 60–120 seconds.

Analysis period T (hours)

0.25 h = 15 minutes; 1.0 h = 60 minutes.

Progression factor PF

PF near 1.0 for average coordination.

Incremental delay factor k (0–1)

Use ~0.50 for typical control and metering effects.

Upstream filtering factor I

Use 1.0 unless you have filtering guidance.

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Approaches

For each approach: volume v, saturation flow s, effective green g. Capacity is computed as c = s·(g/C).

Approach 1 name

Volume v (veh/h)

Saturation flow s (veh/h)

Effective green g (s)

Approach 2 name

Volume v (veh/h)

Saturation flow s (veh/h)

Effective green g (s)

Approach 3 name

Volume v (veh/h)

Saturation flow s (veh/h)

Effective green g (s)

Approach 4 name

Volume v (veh/h)

Saturation flow s (veh/h)

Effective green g (s)

Calculate Delay Fill Example Data Reset

This sample uses a 90-second cycle and typical approach demands.

Intersection delay is a practical performance indicator for construction staging, temporary traffic control, and permanent roadway upgrades. When lane closures, detours, or work-zone speed reductions are introduced, the effective capacity of an approach can change quickly. A delay estimate helps you compare options, document decisions, and communicate impacts to stakeholders using consistent units: seconds of delay per vehicle.

This calculator focuses on approach-based control delay using widely used planning equations. You enter demand volume v, saturation flow s, and effective green g, along with cycle length C. Capacity is computed as c = s·(g/C), and the degree of saturation is X = v/c. As X approaches or exceeds 1.0, queues build and delay rises sharply.

For work-zone planning, start with reasonable saturation flow assumptions that reflect lane widths, heavy-vehicle share, grades, and turning activity. Next, confirm your effective greens: in the field, lost time, pedestrian phases, and coordination can reduce usable green. If you are comparing staging alternatives, keep the analysis period consistent (for example, a 15‑minute peak) and focus on the change in delay and LOS from one scenario to the next.

Worked example (sample inputs): assume a 90‑second cycle, 15‑minute analysis period, and four approaches with the values below. Click Fill Example Data to load the same inputs, then press Calculate Delay to generate approach delays, volume-weighted intersection delay, and LOS.

Deliverables: include the CSV in design packages, and attach the PDF to method statements, submittals, and traffic management plans for quick review.

1) What delay does this tool report?

It reports approach control delay in seconds per vehicle, plus a volume‑weighted intersection average. This supports comparing staging options, timing changes, or demand growth scenarios with consistent metrics.

2) When should I use the HCM-style method?

Use it for general planning, especially when v/c may be near or above 1.0. It combines uniform delay with an incremental component that reflects the rapid rise in queues under oversaturated conditions.

3) When is the Webster-style method appropriate?

Use it mainly for stable, undersaturated operations where v/c is below 1.0. Under heavy congestion it can understate delay, so treat results cautiously when approaches are frequently queued.

4) What is saturation flow and how do I pick it?

Saturation flow is the maximum discharge rate during effective green. Use local guidance if available; otherwise start with typical values and adjust for lane width, grades, turning traffic, heavy vehicles, and site constraints.

5) What does the progression factor PF represent?

PF reflects how well arrivals are coordinated with the green. Values near 1.0 represent average conditions. Higher values increase uniform delay to represent poorer progression or less favorable arrival patterns.

6) Why does delay jump when v/c approaches 1.0?

When demand nears capacity, small fluctuations create persistent queues. Each cycle clears fewer vehicles than arrive, so the queue grows. This nonlinear behavior is why delay increases sharply as v/c reaches or exceeds 1.0.

7) Can I use the results in construction documentation?

Yes. Use the PDF for a concise record and the CSV for calculations and traceability. Always note your assumptions for volumes, effective green, and saturation flow, and validate critical decisions with field observations.

The calculator estimates control delay per vehicle (seconds/vehicle) for each approach, then reports a volume-weighted intersection average: d̄ = Σ(v·d) / Σ(v).

Note: These are planning-level equations. For final design, confirm timings, lost times, lane groups, and field conditions using your local traffic analysis procedure.

1. Choose a calculation method based on your analysis needs.
2. Enter a cycle length and analysis period for the study interval.
3. For each approach, enter demand volume, saturation flow, and effective green.
4. Press Calculate Delay to see results above the form.
5. Use CSV for spreadsheets, or PDF for a shareable report.