Get the Offline ArchiveFree lifetime updates

Terrain Assessment

5 min read

Parent
🗺️
Route Optimization
Choosing the best path for the cargo and conditions
Current
🏔️
Terrain Assessment
Grade limits, surface conditions, bridge capacities

Before committing a loaded convoy, check the steepest grade, the surface, every bridge and the narrowest place on the route: a pair of horses that each sustain a pull of 80 kgf moves a 1,500 kg wagon only up to a 5.7% grade, and up 8-10% they manage about 1,070-1,230 kg gross, so a 1,500 kg wagon needs a third horse. A descent of 10% pushes a loaded wagon forward with 75 kgf even after rolling resistance, so full loads on steep descents need brakes.

Part of Logistics & Load Planning

The grade, surface, bridge and width checks that decide whether a loaded cart or wagon can use a route.

Four Checks Decide Whether A Loaded Wagon Can Use A Route

The parent article lists them. Maximum grade: loaded carts can handle about 8-10% sustained grade; above that, double-team (two teams per cart) or reduce loads; pack animals handle 15-20%. Bridge capacity: check every bridge, since one that holds a person may collapse under a loaded wagon, and know the load limit before you arrive. Road surface: mud needs wider wheels or lighter loads, sand needs wide tires and early-morning travel while the surface is damp and firm, and rock beats up wheels and hooves. Width restrictions: a narrow trail that barely fits a cart is a trap if you meet oncoming traffic, so know where the passing places are.

Other articles in this corpus give lower grade limits: Route Planning has loaded wagons at 7-8% with a comfortable limit of 5%, and Load Capacity says capacity falls by 50-60% on 5-8% grades and 70-80% on 8-12%. The arithmetic below shows why the answer depends on the load.

What You Need

  • A slope measurement — a water level or A-frame. See Grade Calculation.
  • The gross weight of each loaded vehicle.
  • The team’s sustained pull.
  • Bridge load limits — posted or calculated.

Method: Walk The Route

Step 1: Measure the steepest sustained grade Rise over run on each hill. A 5% grade rises 5 m in 100 m.

Step 2: Compute the draft Draft = load × (rolling resistance coefficient + grade). Compare with the team’s pull.

Step 3: Check each descent Net push = load × (grade − rolling resistance). If it is large, plan brakes and a slow descent.

Step 4: Check bridges and surface Read the limit; test the surface; note soft spots.

Step 5: Mark the passing places Where can two vehicles pass?

Worked Example: A 1,500 kg Wagon On Grades

Inputs: gross load 1,500 kg; rolling resistance coefficient 0.05 (good dirt road); each horse sustains 80 kgf of draft; both from Gradient Limits. A kgf is 9.81 N, so 80 kgf is 785 N.

Climbing. Draft = 1,500 × (0.05 + grade).

  • 5%: 1,500 × 0.10 = 150 kgf; 150 / 80 = 1.9 horses.
  • 8%: 1,500 × 0.13 = 195 kgf; 195 / 80 = 2.4 horses.
  • 10%: 1,500 × 0.15 = 225 kgf; 225 / 80 = 2.8 horses.
  • A pair gives 160 kgf. The steepest grade it can climb with 1,500 kg is 160 / 1,500 − 0.05 = 0.057, which is 5.7%.
  • The gross load a pair can pull at 8%: 160 / (0.05 + 0.08) = 1,231 kg; at 10%: 160 / 0.15 = 1,067 kg.

So the parent’s 8-10% holds for a gross load of about 1,070-1,230 kg per pair, and a 1,500 kg wagon needs 3 horses, a third horse added to the pair. This is the “double-team” the parent mentions.

Descending. Net forward push = load × (grade − coefficient).

  • 10% descent, coefficient 0.05: 1,500 × 0.05 = 75 kgf (0.74 kN).
  • 10% descent on a frozen surface, coefficient 0.02: 1,500 × 0.08 = 120 kgf (1.18 kN).
  • 15% descent, coefficient 0.05: 1,500 × 0.10 = 150 kgf (1.47 kN), nearly two horses’ sustained pull, pushing the wagon onto the team.

Bridge. The example bridge in Dead Load vs Live Load allows about 2,200 kg on a single axle. A 3,000 kg wagon with 60% on the rear axle (an assumption) puts 1,800 kg on it, under the limit. The posted limit of a real bridge is the figure to use.

Common Mistakes

  • Using one grade figure for all loads — the limit depends on the load and the team.
  • Looking only at the climb — the descent is where the wagon runs away.
  • Trusting a bridge by its look — a log bridge can be sound for a person and not for an axle.
  • Mud with narrow tires — they sink. Use wide wheels or lighter loads.
  • No passing places — one oncoming cart blocks a narrow track.

Safety

Runaway wagons on descents

A loaded wagon without brakes on a steep descent can overrun and kill its team. Test brakes before the descent, lock a rear wheel with a skid shoe if needed, unload on steep descents if you cannot hold the load, and keep other vehicles well back.

What’s Next