A swept path analysis is the drawing of the entire area a vehicle covers while it turns, not just the line its front wheels follow. On an industrial site it is the step that turns a vehicle length into a yard dimension: how wide the entry must be, how much carriageway a bend needs, how deep the aisle behind a dock has to run. The Slovak templates come from a 2012 study commissioned by the Slovak Road Administration, and they cover forward driving only.
What a swept path analysis actually draws
On a straight run a lorry leaves two tracks. In a bend it does not. The steered axle turns out of its line parallel to the rear axle, the body overhangs the wheels, and the rear wheels roll on a smaller radius than the front, so the vehicle occupies more width in the curve than on the straight. The 2012 study for the Slovak Road Administration states the working rule plainly: the width of lane a combination takes up is the difference between the outer contour radius of the motor vehicle and the inner contour radius of its trailer. A trailer cuts inside the tractor’s path, and that difference is the strip a designer has to find room for.
Underneath sits the Ackermann steering condition. The axes of all wheels meet at one centre of rotation on the extension of the rear axle, and the study writes the relation as cotangent of the inner steered wheel angle minus cotangent of the outer one equals the track between the steering pivots divided by the wheelbase. Real tyres deform sideways under lateral force, so the instantaneous centre of rotation sits a little forward of that geometric point. That is why the curves are simulated rather than drawn with a compass, and why two templates for the same nominal vehicle can differ.
The design vehicle is not the largest lorry on the road
A template is only as good as the vehicle it was drawn for, and the 2012 study picked those vehicles from the national register rather than from a manufacturer’s brochure. It worked through the Police Presidium’s record of 2,498,848 vehicles as at 31 July 2012 and set one selection rule: the representative vehicle in each category had to match roughly 85 per cent of the vehicles in that group. The reason is stated in the study itself. Design elements must not be over-dimensioned for the largest vehicle in a class, which may appear in traffic only exceptionally.
The vehicles that came through that filter were 4.570 m for category M1, 5.505 m for N1, 8.682 m for N2, 11.790 m for a bus and 18,750 mm for an articulated bus, 9.8 m for a solo N3 lorry and 6.160 m for an N3 tractor unit coupled to a category O4 semi-trailer of 13.950 m. Category M2 was dropped because only 699 of its 1,109 records were usable. For an occupier that cuts two ways. The template in a planner’s file is a statistical animal, and the vehicle a carrier actually sends may be longer than it.
What the simulation is run against
Two constraints bound every Slovak curve. The first is the turning ring: a moving vehicle or combination must be able to turn inside a circle with an outer radius of 12.50 m and an inner radius of 5.30 m. The 2012 study took that condition as the basic premise of its simulations and cited government regulation 349/2009 for it. That regulation has since been repealed, and the identical requirement now sits in section 10 of decree 134/2018 of the transport ministry. The figure did not move, the citation did, and a technical report still quoting the old regulation is reading from old drawings.
The second constraint is length. The same decree caps a tractor with a semi-trailer at 16.50 m, a lorry with one trailer at 18.75 m and a combination with two trailers or semi-trailers at 22.00 m; anything beyond is oversize transport under a special-use permit. The templates themselves were produced in Virtual CRASH, with AutoTURN and PC-CRASH named as the alternative tools, at speeds of up to 10 km/h and for changes of direction between 40 and 160 degrees, and issued as DXF overlays per vehicle category.
From a curve to a dimension in the yard
The curves are not an end in themselves. They produce the numbers a site is built to. When the Slovak Road Administration commissioned the University of Zilina in 2019 to prepare the revision of STN 73 6056, the standard for standing and parking areas, the revision derived its dimensions from simulated curves of exactly this kind. Its table of minimum radii gives, for semi-trailer combinations up to 16.50 m, an inner lane radius of 9.00 m, an outer radius of 15.50 m and a carriageway width in the bend of 6.50 m. For drawbar combinations and articulated buses up to 18.75 m the outer radius grows to 16.00 m and the width to 7.00 m, and for semi-trailer combinations up to 18.75 m to 16.50 m and 7.50 m.
The same method sizes the stalls, which is where the truck court inherits its depth. A right-angle stall for a semi-trailer combination up to 16.50 m measures 3.60 m by 17.50 m, with an aisle of 16.00 m in front of it for a vehicle driving in forwards. A dock is a right-angle stall against a wall, so that pair of numbers is the geometry behind an apron. Our post works the same pair forward into a site plan and asks what those metres cost when they are missing. The 2019 study also carries the fire rules through to the parking area: at least one entry to a fenced site has to meet the 3.5 m width and 4.5 m height set by section 82 of decree 94/2004, and a dead-end single-lane access road longer than 50 m needs a turning loop or a turning area at its end.
Where the drawing stops being proof
The decisive limit is written into the 2012 study and is regularly missed. The templates may be used for forward driving. For small vehicles without a trailer they also cover reversing. For combinations they may not, because reversing with those vehicles is individual and depends on the particular driver. Every reverse onto a dock leveller is therefore outside the drawing. A scheme that passes a swept path check at the gate has shown that a lorry can drive in and turn; it has not shown that the same lorry can back onto door 14 while another waits behind it.
The second limit is the age of the rules the drawing feeds. The 2019 study opens by stating that the current wording of STN 73 6056 is the adoption of a Czechoslovak standard of 1987 and no longer reflects the Slovak vehicle fleet. It also attaches a warning to the narrow aisle it tabulates: widths sized for reversing-only entry belong to exceptional cases with insufficient space and where no mass arrival and departure is expected, which is the opposite of a dock face at shift change. The 2012 study closed by recommending that technical conditions be drafted for verifying directional elements and that the design values in STN 73 6101, STN 73 6102, STN 73 6110 and TP 04/2004 be re-examined against the changed fleet.
Frequently Asked Questions
Is it the same thing as a turning circle?
No. The turning circle is a single legal pass or fail, the ring of 12.50 m outer and 5.30 m inner radius in section 10 of decree 134/2018, and it says nothing about a particular site. The swept path is the area a specific vehicle covers on a specific manoeuvre at a specific angle. A combination that satisfies the ring can still fail an entry, a gate radius or an aisle that is too narrow for the width it takes in the bend.
Does the analysis prove a lorry can reverse onto our dock?
No, and this is the most common misreading. The Slovak templates are valid for the forward movement of combinations only; the study excludes reversing for them because the manoeuvre depends on the driver. A dock reverse has to be proved on site with the vehicle a carrier actually runs, or by simulating that one manoeuvre specifically, not by pointing at the standard template.
Which vehicle should the analysis be run for?
At minimum the longest combination that may arrive without a permit: 16.50 m articulated or 18.75 m drawbar. Because the Slovak templates were built on vehicles representing about 85 per cent of each category, testing only the representative vehicle leaves the top of the range untested. Ask for the envelope as well as the average, and for a built-to-suit ask for the fleet the operation will run in five years.
What should an occupier ask for in due diligence?
Three things that make the drawing checkable: which design vehicle it used, which angles of direction change were tested, and which software produced it. A swept path sheet without those three cannot be verified against the operation, and a site with generous clear height and a shallow apron will still hold up every arrival.
Unsure whether the yard on the plan fits the vehicles your carriers actually run? Send us the site layout and we will check it against the envelope.