RE: Notes On EFH

Ref:
R u n g e P ty L td
A .B .N . 1 7 0 1 0 6 7 2 3 2 1
B ris b a n e - H e a d O ffic e
L evel 17
C e n tra l P la z a 1
3 4 5 Q u e e n S tre e t
RE: Notes on EFH B ris b a n e Q ld 4 0 0 0
G PO B ox 2774
B ris b a n e Q ld 4 0 0 1
P h : (6 1 7 ) 3 2 2 1 1 8 8 3
F x : (6 1 7 ) 3 2 2 9 3 7 5 6
1 DEFINITION OF EFH E m a il: r u n g e @ r u n g e .c o m .a u
EFH (Effective or Equivalent Flat Haul) is a ‘relative’ distance

measure used to compare haulage routes. The usual definition
accounts for the effect of grade, however it can be extended to
include road condition and other features that impede the truck
(e.g. rolling resistance, curvature).
The basic principle is to assign an EFH value to a road segment that is the length of an equivalent
flat segment. The most intuitive measure of ‘equivalence’ is Travel Time. That is EFH is the
distance the truck would travel on an ‘idea’ flat segment in the same time it actually takes to travel
the graded segment.
2 USAGE OF EFH
EFH is used as a comparative measure of haulage between routes, schedules and schedule periods.
The purpose for which the EFH will be used should have an impact on how it is calculated.
2.1 Estimating Work

Multiplying EFH by Tonnes (and accumulating) gives a measure of total work, similar to
∑(Tonne*Kms) only with the Kms adjusted to account for different road conditions and
therefore a more useful comparative measure. For this usage it may be more appropriate to
use the EFH for the loaded and empty return trips separately. This equates to only using the
loaded EFH as the tonnage on the return trip is zero and therefore does not contribute to the
total.
2.2 Estimating Truck Numbers

The average tonnage weighted EFH (∑Tonne*EFH/∑Tonne) for a period is sometimes used
to estimate the changing trucking requirements. This average times the required production
gives an absolute measure. This is similar to using Travel Time and should use the EFH for
the full cycle (loaded and return trip) times the tonnes hauled in the cycle.
The issue with using EFH, or Travel Time, to estimate truck numbers is that they do not
correctly account for the component of the truck’s working time spent loading, dumping and
queuing. In fact if the average haulage distance is changing between periods, as is typical
across the life of a pit, then these measures have a bias. For shorter hauls the delays form a
larger percentage of the total Cycle Time.
-2-
The advantage of using EFH or Travel Time is that they can more
easily be estimated. Generally an adjustment is made to the available
truck hours to account for the average delays.
It is preferable, however, to use a method for estimating truck hours that accounts for the
full Cycle Time. For example TALPAC Cycle Times and Average Payload or alternatively
Truck Productivity which is derived from them.
3 CALCULATION OF EFH
There are various methods used to calculate EFH, each requiring a different level of effort with
subsequent gain of resolution.
3.1 EFH Grade Range Factors

One simplified method of estimating EFH for a segment is to have a look-up table of EFH
Factors for various ranges of road grade. The VULCAN Software has a module that uses this
method.
The user needs to estimate the EFH Factor for a ranges of grades (e.g. 0-2%, 2-4%, 4-6% etc.)
covering both the loaded and return trip. This is normally done by surveying travel times over
typical segments.
The advantage of this method is that once the factors are determined an EFH can be
calculated for many haulage routes in a systematic way (e.g. script) without requiring the
running of any simulations in TALPAC.
The disadvantages include that this method does not account for the initial or final speed or
segment lengths, hence acceleration and deceleration.
3.2 Nominal Flat Speed

For this method a nominal ‘average’ flat speed is estimated from surveys and TALPAC
simulations. This speed should be typical of the truck and haulage segments and usually is an
average of loaded and unloaded speed.
To determine the EFH of a haul route the TALPAC Travel Time over the route is multiplied
by the Nominal Flat Speed.
This method could be improved by considering the loaded and return trip separately with
different Nominal Flat Speeds for each. It does not, however, account for the effects of
varying segment lengths and road conditions.
3.3 TALPAC Flat Simulations

The most accurate method to estimate EFH is to run 2 TALPAC simulations and compare the
Average Speeds.
The normal TALPAC simulation will give an estimate of actual Travel Time. For comparison
all grades in the haul route are changed to zero and a second simulation run to determine the
Average Flat Speed.
The EFH of the route is the total Distance times the ratio of the Average Flat Speed over the
Average Speed. As the distance is the same in both simulations this ratio is equivalent to the
ratio of the Travel Times.
-3-
As a further refinement the Rolling Resistance values for the reference

simulation could be reset to some nominal base value to account for
differences in road surfaces.
This method requires considerable more work than the previous methods. RUNGE is however
considering including an estimate of EFH in a future version of TALPAC.
4 EXAMPLES
A simple example may help to illustrate the issue of bias in using EFH for estimating Truck
numbers against a method that uses Cycle Time or Truck Productivity.
Consider a trivial example of a single ramp.
 Grade is 10% out of the pit.
 Maximum Speed is 40 km/hr.
 On flat a loaded or empty truck averages around 30 km/hr taking into account acceleration
and deceleration.
 Loaded going up the ramp the truck averages 10 km/hr.
 Loading, dumping and queuing are on average 3 minutes per cycle.
 For Period 1 the ramp is on average 1000m, for Period 2 it is 2000m.
Period Distance Delays Travel Time Cycle Time Loaded EFH 2-Way EFH
1 1000 3 8 11 3000 4000
2 2000 3 16 19 6000 8000
Ratio 2 1 2 1.7 2 2
According to the Cycle Time increase, 1.7 times the working truck hours (and hence trucks) are
required in Period 2 over Period 1. EFH overestimates this at twice the truck hours.
This example also shows that the 2-Way EFH is not double the 1-Way EFH. This is because the
effect on Travel Time of the grade is more significant for a loaded truck. In this example going
down the ramp has an EFH Factor of 1 whilst going up has and EFH Factor of 3.
In the above example Loaded EFH shows the same increase as 2-Way. This is not necessarily the
case as the longer haul may have a different average profile and therefore speed. For example
consider a variation on the above example when the addition 1000m is flat haul. The average loaded
speed would increase to 20 km/hr with the results below.
Period Distance Delays Travel Time Cycle Time Loaded EFH 2-Way EFH
1 1000 3 8 11 3000 4000
2 2000 3 9.4 12.4 3500 5500
Ratio 2 1 1.2 1.1 1.2 1.4
-4-
5 RECOMMENDATIONS
We believe the use of ∑ Tonnes * Loaded EFH is a reasonable relative
indicator of total haulage work, with an advantage over Tonne Kms in that it adjusts for differences
in the haulage profiles. In this usage the one way loaded EFH times the total delivered Tonnes is
more appropriate than the round trip EFH.
Truck requirements are better estimated using full Cycle Times, or Truck Productivities that are
derived from them, than EFH or Travel Times. The discussion and examples above demonstrate
how EFH may give misleading results if the average haulage lengths vary from period to period.
Whilst the detailed method of calculating EFH using pairs of TALPAC simulations will give the
best results, we suggest some simple trials to see if Nominal Flat Speeds can be determined that
give reasonable close estimates of EFH by the more simple method of multiplying the TALPAC
Travel Time by the Nominal Flat Speed.

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EFH (Effective or Equivalent Flat Haul) is a ‘relative’ distance

2.1 Estimating Work

2.2 Estimating Truck Numbers

3.1 EFH Grade Range Factors

3.2 Nominal Flat Speed

3.3 TALPAC Flat Simulations

As a further refinement the Rolling Resistance values for the reference

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