Swept Path Analysis: The Complete Guide for Planners
Swept path analysis is a fundamental tool in traffic and site planning. It shows the area a vehicle occupies during maneuvers – essential for designing roads, parking lots, and access routes. This article walks through the basics and answers a question most online sources avoid: why you cannot freely download the official design vehicle dimensions, and what legal alternatives exist.
What is a Swept Path?
A swept path describes the area covered by all parts of a vehicle during a turning maneuver. Unlike a simple turning circle, it accounts for:
- Vehicle overhangs front and rear
- Vehicle width including mirrors
- Trailers and semi-trailers on commercial vehicles
The Ackermann Geometry
The physical basis for swept paths is Ackermann steering geometry. Developed by Rudolph Ackermann in 1817, it describes the principle that during a turn, wheels must travel along different circular paths. The inner wheel travels a smaller circle than the outer one. The steering geometry ensures all wheels rotate around a common center point.
Key Vehicle Parameters
For swept path calculation, these dimensions are critical:
| Parameter | Description |
|---|---|
| Wheelbase | Distance between front and rear axle |
| Front Overhang | Vehicle front to front axle |
| Rear Overhang | Rear axle to vehicle end |
| Width | Total vehicle width |
| Turning Circle | Diameter of minimum turning circle |
| Steering Angle | Maximum steering angle of front wheels |
Applications
Swept path analysis is needed for:
- Intersection design and curve radii
- Fire truck access verification
- Parking lot and garage planning
- Loading dock design for trucks
- Bus turnaround loops
- Garbage truck turning radii
- Dead-end turnarounds
Standards and Design Vehicles: What Google Doesn't Tell You
Different countries publish their own design vehicle standards:
| Country | Standard | Publisher |
|---|---|---|
| USA | AASHTO Green Book design vehicles | AASHTO |
| USA (fire) | NFPA 1901 / IFC | NFPA / ICC |
| UK | Design Manual for Roads and Bridges (DMRB) | National Highways |
| Germany (general) | RBSV 2020 | FGSV Verlag |
| Germany (fire) | DIN EN 14043 / DIN 14502 / DIN 14090 | DIN Media GmbH |
| Australia | AS 2890 series | Standards Australia |
What is rarely mentioned: all of these are copyrighted publications. The tables of design vehicle dimensions and the swept path templates are not free downloads. In Germany, full reproduction of the RBSV 2020 tables would violate the database producer right under § 87b UrhG. In the US, the AASHTO Green Book and NFPA standards are similarly protected. That is exactly why a Google search for "RBSV 2020 dimensions" or "NFPA 1901 fire truck specs" returns only fragments and contradictory values.
Three legal ways to obtain design vehicle dimensions
1. Buy the standard.
- RBSV 2020 from the FGSV Verlag (~€53 at fgsv-verlag.de)
- AASHTO Green Book (~$400)
- NFPA 1901 (~$250) – read-only at nfpa.org/freeaccess
- IFC (~$150) – read-only at codes.iccsafe.org/free-resources
- DIN EN 14043 / DIN 14502 (low three-digit EUR each at dinmedia.de)
2. Use CAD software with embedded standards. Several professional CAD packages license the standards and ship the design vehicles as part of their subscription:
- Autodesk Vehicle Tracking
- AutoCAD Civil 3D (with Country Kit)
- Bentley OpenRoads Designer
- BricsCAD Pro
- Vectorworks Landschaft
- CARD/1
- ProVI
- RIB iTWO civil
- Trimble Novapoint
3. Use public legal maxima plus manufacturer data. For private projects, feasibility studies and pre-design, the publicly available statutory maxima are usually enough:
- Germany – § 32 StVZO: vehicle length up to 12.00 m, width 2.55 m, height 4.00 m; semi-trailer truck up to 16.50 m
- Germany – § 32d StVZO: every street-legal vehicle must turn within an outer radius of 12.50 m and an inner radius of 5.30 m (BO-Kraftkreis)
- US: state DOT design vehicle specifications are typically published by the state DOT and freely accessible
These statutory values are public domain. Combined with manufacturer data sheets (Mercedes-Benz, MAN, Volvo, Pierce, E-ONE, Magirus, Rosenbauer) they provide a defensible basis for the vast majority of planning situations.
When Do You Actually Need the Licensed Standard?
| Situation | Recommendation |
|---|---|
| Tendered public project explicitly referencing RBSV / AASHTO / DMRB | Buy the standard or use licensed CAD software |
| Private developer / pre-design / feasibility | Statutory maxima + manufacturer data sheets |
| Education / research / journalism | Citing individual values is usually fine; full table reproduction is not |
| In doubt | Written question to the responsible planning office before starting |
Many municipalities and federal agencies explicitly require the named standard in tenders. Check before you start planning – it saves expensive corrections later.
Conclusion
Swept path analysis is indispensable for safe traffic planning. Knowing the legal landscape lets you choose deliberately between licensed standards and free alternatives – avoiding both unnecessary licensing costs and expensive rework during permit review.
PathSweeper is currently available as a demo and ships with default vehicles based on statutory maxima and publicly available manufacturer datasheets – ideal for pre-design, feasibility studies and private projects. Licensed standard content is planned for a future full release.
Related Guides
- RBSV 2020 Design Vehicles Explained – the reference table of German design vehicles plus the three legal ways to access the official numbers.
- Fire Truck Access per DIN 14090 – minimum dimensions, aerial ladder DLK 23/12, setup areas and the DIN licensing question.
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