A route survey (güzergâh etüdü) is an on-site inspection of the road an oversize or heavy load will travel, from the loading point to the delivery point. Overpass and power line heights, junction turning radii, gradients, ground conditions and bridges are measured; the findings become a report showing the obstacles, solutions and an alternative route, and form the basis of the permit application.
What does a survey try to prove?
A survey has a single question: can the chosen vehicle combination, with its load, pass safely through every point on the road? The answer cannot be read fully from a map. A newly built traffic island, a low traffic sign or a power line sagging in the heat can close a route that looks perfect on paper. That is why a survey runs on two levels: a desk-based preliminary study and on-site driving and measurement.
Which obstacles are measured?
| Criterion | Points checked | Possible solution |
|---|---|---|
| Vertical clearance | Overpasses, tunnels, power and telecom lines, sign gantries, tree branches | Temporary lifting of the line, a lower trailer, a side road |
| Horizontal clearance | Bridge railings, toll booths, traffic islands, building corners | Temporary removal, controlled use of the opposite lane |
| Turning radius | Junctions, roundabouts, sharp bends | Swept path analysis, steerable trailer, temporary fill |
| Longitudinal gradient and break-over | Ramps, humps, level crossings | Pusher tractor, hydraulic height adjustment |
| Cross slope | Superelevation, damaged shoulders | Speed limit, recalculation of load balance |
| Ground and structures | Bridges, culverts, unpaved site roads | Structural check, steel plates, bypass |
Assessing bridges requires separate expertise; the method is explained in the bridge and culvert check entry, and overcoming lines and overpasses in the power lines and overpasses entry.
How is a survey carried out step by step?
- Fix the data: The packed dimensions, weight and centre of gravity of the load; the loaded height, width, overall length and axle loads of the vehicle combination.
- Identify candidate routes: Select two or three options using maps, satellite imagery and records of previous moves.
- Drive the route: Travel the route from start to finish with a survey vehicle. Each obstacle is measured with a laser meter or total station, and its coordinates and photo are recorded; complex junctions are filmed by drone.
- Check the swept path: The area swept by the long combination at critical junctions is verified with software or with a template on site.
- Involve stakeholders: Temporary works and timing are discussed with the electricity distribution company, the municipality, the railway operator, the port and the KGM (General Directorate of Highways) regional directorate.
- Write the report: List of obstacles, a solution for each, required temporary works, escort arrangement and alternative route.
Who does it, and when?
The survey is usually carried out by the engineers of the transport organiser or heavy haulage company; on large projects, an independent cargo surveyor also inspects the route on behalf of the insurer or the buyer. The cargo owner is responsible for the accuracy of the dimensions and weight it provides.
Timing has three stages: a rough preliminary survey before the quotation, a detailed survey before the permit application, and a final check a few days before the move. The detailed survey is a direct input to the KGM special permit application. Under Article 128 of the Highway Traffic Regulation (Karayolları Trafik Yönetmeliği), a permit for a loaded move is issued separately for each trip, specifying the route and time of transport; a vehicle that sets out without a permit or in breach of its conditions is taken off the road.
Why should the alternative route be in the report?
Roadworks, an accident or an unexpected closure can make the permitted route unusable on the day of the move. Because the permit is tied to the route, changing route on the way at will is not possible. If the alternative road has been surveyed in advance and, where necessary, entered in the permit, the vehicle continues with plan B instead of waiting.
Common mistakes
- Measuring only the height of the load and not taking into account the trailer deck height and the suspension's loaded settlement.
- Carrying out the survey in dry weather and overlooking an unpaved site road that will soften in rain.
- Forgetting that power lines sag more in summer heat.
- Making the move months after the survey and missing a traffic island or sign installed in the meantime.
Survey data is the common source for vehicle selection, the permit file and the escort plan in oversize and heavy cargo transport.