Model taper needs for shifting traffic safely. Check buffers, cone counts, and sign spacing quickly. Plan smarter temporary control layouts before crews reach site.
This graph shows how the selected scenario responds to changing speed. It compares active taper length, longitudinal buffer, and advance sign spacing.
| Scenario | Speed (mph) | Closure | Environment | Active Taper (ft) | Buffer (ft) | Sign Spacing (ft) | Total Devices | Queue Risk |
|---|---|---|---|---|---|---|---|---|
| Example 1 | 25 | Shoulder Work | Urban | 63 | 151 | 100 | 10 | Low |
| Example 2 | 45 | Full Lane Closure | Urban | 540 | 358 | 180 | 31 | Moderate |
| Example 3 | 60 | Full Lane Closure | Rural | 720 | 584 | 480 | 39 | Very High |
Examples are sample planning scenarios. Always reconcile field conditions, agency rules, and approved details before use.
1) Lane closure taper length
L = W × S² / 60 when speed is 40 mph or less.
L = W × S when speed is above 40 mph.
Here, L is taper length in feet, W is lane width in feet, and S is speed in mph.
2) Shift taper length
The same taper equation is applied using lateral shift width instead of full lane width. This supports lane shifts and shoulder activity layouts.
3) Longitudinal buffer estimate
Buffer = 1.47 × S × t + S² / (30 × (f + G))
where t is reaction time, f is friction factor, and G is grade as a decimal.
4) Advance sign spacing
Urban spacing uses max(100, S × 4).
Rural spacing uses max(350, S × 8).
5) Channelizing device spacing
Taper spacing uses approximately the speed in feet.
Tangent spacing uses approximately twice the speed in feet.
6) Queue risk indicator
v/c = hourly traffic demand ÷ open lane capacity.
The result flags low, moderate, high, or very high queue risk during closure.
It estimates taper lengths, longitudinal buffer space, advance sign spacing, channelizing device counts, basic work area density, and a demand-to-capacity queue risk check for temporary traffic control planning.
For lower speeds, taper length uses lane or shift width multiplied by speed squared, divided by sixty. For higher speeds, taper length uses width multiplied directly by speed.
Higher speeds increase reaction distance and braking distance. That means the approach needs more recovery space before the active work area begins.
Use lane shift when traffic remains on the same carriageway but moves sideways around the work. Use full lane closure when one lane is fully taken out of service.
The estimate divides taper and tangent lengths by typical spacing rules based on speed. It then adds a starting device so the setup begins clearly at the taper entry.
Yes. Traffic demand does not change taper geometry directly here, but it changes the queue risk indicator by comparing demand to the capacity left after the closure.
No. This tool supports planning and quick checks. Final layouts must still follow the governing standard drawings, contract documents, and project-specific approvals.
Yes. The page includes buttons to download a CSV of the current results, a CSV of example scenarios, and a PDF summary for sharing or recordkeeping.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.