Calculator inputs
Designed for site planning, zoning checks, and early construction feasibility.
Driving, 15 minutes, detour 1.3.
Example data table
These sample scenarios show how detour and buffer reduce a theoretical travel distance into a planning radius.
| Site | Facility | Mode | Speed (km/h) | Time (min) | Delay (min) | Detour | Buffer (%) | Radius (km) | Area (km²) | Est. Pop |
|---|---|---|---|---|---|---|---|---|---|---|
| Parcel A | Clinic | Walking | 5.0 | 20 | 2 | 1.20 | 5 | 1.188 | 4.430 | 28,796 |
| Parcel B | Hospital | Driving | 45.0 | 15 | 3 | 1.35 | 7 | 6.200 | 120.763 | 507,204 |
| Parcel C | ER | Ambulance | 60.0 | 10 | 1 | 1.25 | 5 | 6.840 | 146.981 | 440,944 |
| Parcel D | Clinic | Cycling | 18.0 | 25 | 2 | 1.30 | 6 | 4.989 | 78.202 | 398,829 |
| Parcel E | Hospital | Driving | 35.0 | 30 | 5 | 1.40 | 8 | 9.583 | 288.525 | 721,312 |
Formula used
- Effective time (min) = max travel time − delay allowance
- Network distance (km) = speed (km/h) × (effective time ÷ 60)
- Service radius (km) = (network distance ÷ detour factor) × (1 − buffer%)
- Coverage area (km²) = π × radius²
- Estimated population served = coverage area × population density
Detour factor approximates route inefficiency. Buffer margin adds conservatism for safety, terrain, access control, and uncertainty during early design.
How to use this calculator
- Select a travel mode that matches your service expectation.
- Enter max travel time for compliance checks or service goals.
- Add delay allowance for gates, congestion, and dispatch time.
- Set detour factor to reflect road/path layout efficiency.
- Use a buffer margin to stay conservative during planning.
- Optional: add density to estimate population served.
- Optional: add site population and target per facility for counts.
- Press
Calculate access radiusand review results. - Download CSV or PDF to attach to planning notes.
For detailed network analysis, validate outputs against GIS routing and local standards.
Access radius in construction planning
Healthcare access is a measurable constraint in master planning and community impact studies. This calculator converts travel assumptions into a practical service radius you can draw around a site. Use it to test whether a proposed parcel can reach a clinic or hospital within your target minutes. Early checks reduce redesign risk, support stakeholder conversations, and help compare options using consistent criteria across phases and budgets. It also supports preliminary ambulance response planning.
Detour and delay adjustments
Straight line distance rarely matches real routes, especially near barriers and limited crossings. The detour factor models road curvature, topography, and access control by shrinking a network distance into a radius. The delay allowance covers gates, congestion, dispatch staging, and security checks that consume time before movement. Together they prevent overstated coverage and make outputs easier to defend during reviews and audits.
Population demand signals
When you add population density, the coverage area becomes a proxy for potential demand and service equity. Multiply area by density to estimate people who could reach care within the time threshold. This supports capacity discussions, referral planning, and phased construction. Pair the estimate with service standards, then refine later with census layers, land use forecasts, and catchment modeling for accuracy. Use sensitivity runs to see best and worst cases.
Documentation and reporting
Outputs are structured for design notes, feasibility reports, and approvals. Record assumptions, then export CSV for spreadsheets or PDF for submittals. Include radius, network distance, and area on a constraints plan, and state the detour and buffer values used. For multi site programs, keep one scenario per row to compare equity, response time, and coverage consistency across phases and contractor packages.
Quality checks and limitations
Treat results as a screening tool, not final routing analysis. Validate speed against peak and off peak conditions, and select detour using local street grids, corridor access, and observed turning restrictions. If a river, railway, steep grade, or security perimeter exists, increase detour or delay. For critical facilities, confirm with GIS isochrones, field checks, emergency protocols, and local codes. Document why assumptions were chosen.
FAQs
What does the detour factor represent?
It represents how much longer real routes are than straight line distance. A value of 1.30 means paths are about 30% longer, so the radius is reduced to stay realistic.
How should I pick an average speed?
Use a conservative speed for the dominant travel mode and typical conditions. For driving, consider intersections and congestion. For walking or cycling, use realistic speeds for the expected user group and terrain.
Why add a delay allowance?
Delays capture time lost before travel, such as gate access, security checks, dispatch staging, or waiting for transport. Subtracting delay from the time budget prevents overly optimistic coverage.
Can I estimate population served?
Yes. Enter population density to estimate served people as area multiplied by density. Treat it as a screening estimate and refine later with GIS, census layers, and land use forecasts.
Why does the buffer margin reduce the radius?
The buffer applies a safety margin for uncertainty in traffic, access control, or data quality. A 5% buffer shrinks the radius so the plan remains achievable under less favorable conditions.
Is this suitable for final compliance submissions?
It is best for early planning and comparisons. For final compliance, validate assumptions, confirm travel times with routing or GIS isochrones, and check local standards and agency requirements.