Determining the Measured Mile for Lost Productivity Claims
Proving and quantifying lost productivity is one of the most contentious and controversial areas in construction claims and disputes. This task involves processing data for work completed and it involves work-hours study, productivity calculation, baseline establishment, causation study and measuring productivity loss. Productivity can be measured as a ratio between the units of work accomplished (output) and the units of time or efforts expended (input). In this article, productivity is defined as the ratio of input to output but the inverse is also commonly used.
There are many methods to quantify productivity loss, but the measured mile method is by far the most preferred for computing loss productivity in the construction industry. The measured mile method compares the productivity of identical activities which are segregated into unimpacted and impacted periods of the project. The difference is then asserted to represent the loss of productivity from the impacts.
In this article, we shall introduce Zink’s method to calculate the measured mile. Zink developed a procedure to ascertain the measured mile, by isolating a reasonable linear or near-linear portion in the labour hours – progress curve, which represents the most efficient productivity. This measured mile productivity is then taken to represent the productivity from no impacts or minimal impacts period.
On a municipal sewer upgrade project, a contractor was to replace and install 15-inch vitrified clay pipe (VCP) sewer pipes. According to the baseline schedule, the installation was planned to be performed in a dry season. Because of delays experienced in preceding work, the contractor actually performed 15: VCP replacement work in a stormy season and installation was hampered by muddy site conditions. Further, unmarked utilities and conflicts were encountered in multiple locations. The contractor had to skip those areas and mobilize back later after a resolution was provided by the engineer of record. The production data compiled from contemporaneous documentation has been summarized in Table 1, and it can be seen that the impacts were pervasive.
Zink’s Measured Mile Procedure – Step by Step Guide
The procedure Zink proposed include:
Plot the actual labour man-hours expended versus the corresponding percentage of work completion.
Exclude the first and last 10% from the analysis because the productivity during these periods may be impacted by “build-up” and “tail-out” effects.
Identify as the measured mile a linear or near-linear portion showing the most efficient rate of progress in the middle 80% of the curve.
A continuous period of time in which the most efficient productivity is uniform or near-uniform.
Measured mile to be impact-free.
Step 1: Excluding the first 10% and last 10% of total labour hours
The first and the last 10% are excluded from the analysis. The rows in the below table highlighted in grey, Work Day 1 to 4 and Work Day 32 to 35 are excluded from the analysis.
Step 2: Identification of measured mile period from the intermediate 80% of the labour hours
Analysis of the actual labour hours focuses on the intermediate 80% of the labour hours. For consecutive daily productivities, Day 18 to Day 21 are identified as the measured mile period.
Step 3: Calculating measured mile productivity
The resulting measured mile productivity is calculated to be 3.35 hr/lf, which is the average of the following values highlighted in yellow:
Measured mile productivity = Average of (2.73+3.43+3.24+4.00) = 3.35hr/lf
In practice, a measured mile period or segment with uniform or nearly uniform productivity may not exist due to pervasive disruptions. Zink did not define how to identify from the chart the linear portion that would represent the most efficient rate of progress. Hence this method of identifying the measured mile is subjective.
Being able to lead in all stages of the development process is equally as important as being able to lead all the parties involved. RPM leads the Design Team, Consultants, Contractors and sometimes the Client too so that the vision for the project can be attained. The only thing that RPM will not do, is push papers.
 2015 AACE® INTERNATIONAL TECHNICAL PAPER – CDR.1967 Determining the Measured Mile for Lost Productivity Claims by Dr. Tong Zhao, PE PSP and J. Mark Dungan Zink, D.A., 1986, The measured Mile: Proving Construction Inefficiency Costs, AACE International Cost Engineering Journal, 28(4), Pages 19-21, AACE International, Morgantown, WV Zink, D.A., 1990, Impacts and Construction Inefficiency, AACE International Cost Engineering Journal, 32(11), Pages 21-23, AACE International, Morgantown, WV