The short answer
Lead is the horizontal distance material is moved from where it is dug or loaded to where it is placed. Lift is the vertical height it is raised. A rate for earthwork or for supplied aggregate always assumes a certain lead and lift, and anything beyond that is paid as extra haulage. For crushed stone, lead from the plant to the road head is usually the largest single part of the delivered price.
The two words appear in almost every item of a bill of quantities for earthwork and material, usually in a phrase such as "with all leads and lifts". That phrase decides who pays for the distance, so it is worth knowing exactly what is being agreed.
01Lead
Lead is measured along the shortest practicable route a vehicle can take, not in a straight line on the drawing. For earth moved from a cutting to an embankment, it is taken between the centre of the mass that was dug and the centre of the mass that was placed. That is the average lead, and it is the distance the rate is built on.
Many schedules of rates include a short initial lead in the basic item. Under the Central Public Works Department's specification, ordinary excavation carries an initial lead of 50 m and a lift of 1.5 m, and movement beyond that is measured and paid as a separate item. Highway contracts more often write "all leads and lifts", which puts the whole distance, whatever it turns out to be, inside the contractor's rate.
02Lift
Lift is the height through which material has to be raised, measured from the level it is dug at to the level it is placed at. In manual and small-machine work it is counted in steps of 1.5 m. On mechanised highway work it mostly disappears into the haul, since a tipper climbs a ramp instead of anyone lifting anything, but it comes back in deep foundation pits, in filling behind high structures and in quarry benches, where every tonne has to be brought up out of the pit.
03Why "all leads" is a risk you should price
A contractor who accepts all leads has taken on the distance to a borrow area or a quarry that may not yet be approved. If the approved source turns out to be 35 km away where the estimate assumed 12, the rate does not move and the haulage bill triples.
- Identify the likely sources before the bid, and drive the route as a loaded truck would have to: bridges, villages, weight restrictions.
- Work out the tonnes that will come from each source, and the average lead for each.
- Price haulage on the weighted average, with the monsoon detour if there is one.
- Where the contract allows a lead chart to be approved, get it approved early and in writing.
04Lead and the price of stone
Crushed stone is cheap at the plant and heavy on the road. Haulage is charged by weight and distance, so its cost rises in a straight line with lead, while the cost of making the stone stays the same. Somewhere along that line the freight becomes larger than the material.
| Lead | Trips | Tonnes delivered | Tonne-kilometres |
|---|---|---|---|
| 10 km | 9 | 162 | 1,620 |
| 20 km | 5 | 90 | 1,800 |
| 40 km | 3 | 54 | 2,160 |
| 60 km | 2 | 36 | 2,160 |
Same assumptions as the table in the cycle time article. The truck costs about the same for the day in every row.
The truck and its driver cost nearly the same for the shift whatever the lead. At 10 km that cost is spread over 162 tonnes. At 60 km it is spread over 36. Freight per tonne has gone up four and a half times while the stone has not changed at all. The working is in how many tippers a job needs.
05What to give a supplier
A delivered rate cannot be quoted without the lead, and "near the bypass" is not a lead. Give the chainage or a map pin for the road head, say whether the last stretch is surfaced, and say whether the tipping point moves along the alignment as work progresses. If it does, ask for the rate as a base figure plus a rate per tonne-kilometre, so that neither side is guessing at the average.