Time and Motion Studies: Measuring and Improving Work Efficiency
Time and motion studies are the original tools of industrial engineering. Frederick Winslow Taylor pioneered time study in the 1880s, measuring how long it took workers to perform specific tasks and identifying the one best way to do each job. Frank and Lillian Gilbreth added motion study, analyzing the fundamental movements of work and eliminating unnecessary motions. Together, these techniques form the foundation of work design and productivity improvement.
The principles established by Taylor and the Gilbreths remain relevant over a century later. Every time a company reduces cycle time, eliminates wasted motion, or standardizes work methods, it is applying the legacy of time and motion study. Modern techniques have evolved, but the fundamental objective remains the same: measure work systematically, analyze it critically, and design better methods.
Methods Analysis
Before measuring work, understand the work. Methods analysis examines how work is performed to identify opportunities for improvement.
Process Charts
The process chart is a graphical representation of the sequence of steps in a work process. Standard symbols distinguish between operations (circle), inspections (square), transportation (arrow), storage (triangle), and delays (D). Each step is classified, timed, and documented.
The flow process chart documents the path of a product or person through the process. It reveals unnecessary transportation, waiting, and inspections. A typical office process has 30 to 50 percent inspection and delay steps — each one an opportunity for elimination.
Operation Charts
The operation chart focuses on the operator’s activities at a single workstation. Left-hand and right-hand charts document what each hand does during the work cycle. They reveal opportunities to balance hand work, improve motion patterns, and reduce fatigue.
The principles of motion economy guide methods improvement. Two hands should begin and complete their motions simultaneously. Hands should not be idle except during rest periods. Motions should be confined to the lowest classification possible — finger motions are faster and less fatiguing than whole-arm motions.
Micro-Motion Study
Micro-motion study analyzes work at the level of basic motions using therbligs — the 17 fundamental motion elements identified by Frank and Lillian Gilbreth. Therbligs include search, select, grasp, transport empty, transport loaded, position, assemble, use, disassemble, inspect, pre-position, release load, and others.
Effective therbligs directly advance the work — grasp, transport loaded, position, assemble, use. Ineffective therbligs do not — search, select, pre-position, hold, delay. Methods improvement eliminates or reduces ineffective therbligs. The work design and ergonomics article covers how therblig analysis integrates with workplace design.
Time Measurement
Measuring how long work takes requires systematic techniques.
Stopwatch Time Study
Direct time study using a stopwatch is the most common work measurement method. The analyst observes the operator, records the time for each work element over multiple cycles, rates the operator’s performance, and computes standard time.
Performance rating adjusts observed time to the normal pace. A rating of 100 percent is normal — the pace a qualified operator can maintain all day without excessive fatigue. A rating of 120 percent means the operator is working faster than normal. The normal time equals observed time multiplied by the rating factor divided by 100.
Elemental Breakdown
Work cycles are divided into elements — distinct steps with clear beginning and end points. Short elements under 0.03 minutes are grouped. Manual elements are separated from machine elements because they have different variability and improvement potential.
Sufficient cycles must be timed to achieve statistical accuracy. The required number of cycles depends on the allowable error and the variability of the element times. For plus or minus 5 percent accuracy at 95 percent confidence, 10 to 30 cycles are typically needed.
Standard Time Calculation
Standard time equals normal time plus allowances. Allowances include personal time, fatigue, and unavoidable delays. Personal allowance of 5 to 7 percent covers restroom breaks and drinking water. Fatigue allowance of 4 to 10 percent depends on the physical demands of the work. Delay allowance of 2 to 5 percent accounts for interruptions and minor machine adjustments.
Total allowances of 15 to 20 percent are typical. The standard time equals normal time divided by 1 minus the allowance fraction. If normal time is 2.0 minutes and total allowance is 15 percent, standard time is 2.35 minutes.
Predetermined Motion Time Systems
PMTS uses standard time values for basic motions to build standard times without stopwatch timing.
Methods-Time Measurement
MTM is the most widely used PMTS. It provides standard times for basic motions — reach, move, turn, grasp, position, release, and disengage — based on the distance, weight, and type of motion. A reach motion of 20 inches to an object jumbled with others has a standard time of 0.044 minutes.
MTM-1 is the most detailed and accurate level. MTM-2 and MTM-3 are simplified versions with fewer motion categories and larger time increments, suitable for longer cycles. MOST — Maynard Operation Sequence Technique — is a faster PMTS that groups motions into sequences of general move, controlled move, and tool use.
Advantages of PMTS
PMTS does not require stopwatch timing or performance rating. It can be applied from a video recording or even from a description of the work method. It provides consistent, reliable time standards that are not influenced by operator performance differences.
PMTS is particularly valuable for new operations where no production data exists. Standard times can be developed before production begins, enabling accurate cost estimating and labor planning.
Standard Data Systems
Standard data systems build time formulas for families of similar work.
Developing Standard Data
Standard data combines time study data and PMTS values into formulas that predict time based on key variables. A drilling standard might predict setup time as 5 minutes plus 0.5 minutes per hole, with adjustments for hole depth and material hardness.
Standard data accelerates standard development and ensures consistency across similar operations. Once standard data is developed for a class of work, new operations can be timed by simply measuring the key variables and plugging them into the formula.
Maintaining Standard Data
Standard data must be maintained as methods and technology change. Periodic audits verify that the time formulas still match actual work. Standard data that is not maintained becomes increasingly inaccurate and loses credibility with operators and management.
Applications of Work Measurement
Standard times have many uses beyond setting labor standards.
Production Planning
Standard times enable capacity planning. If each unit requires 2.5 hours of labor and the plant has 10,000 available hours per week, the maximum production rate is 4,000 units per week. The manufacturing planning article discusses how standard times feed into production plans.
Cost Estimating
Accurate labor costs require accurate time standards. A cost estimate for a new product starts with the estimated standard time for each operation, multiplied by the labor rate. Material costs, overhead allocation, and profit margin are added to determine the selling price.
Incentive Systems
Time-based incentive systems pay workers based on output relative to standard. An operator who produces at 120 percent of standard earns 20 percent bonus pay. Properly designed incentive systems increase productivity by 20 to 40 percent. Poorly designed systems create quality problems and adversarial relationships.
Work Sampling
Work sampling is a technique for estimating the proportion of time spent on different activities without continuous observation.
Methodology
Work sampling involves making random observations of workers or equipment and recording the activity at each observation. After hundreds or thousands of observations, the proportion of observations in each category estimates the proportion of time spent on that activity.
The accuracy of work sampling depends on the number of observations. For plus or minus 5 percent accuracy at 95 percent confidence, 400 observations are needed if the activity proportion is approximately 50 percent. For activities that occur less frequently, more observations are needed.
Applications
Work sampling measures utilization — the percentage of time workers spend on productive activities. Typical direct labor utilization in manufacturing is 50 to 70 percent. The remaining time is spent on personal activities, waiting, and indirect tasks.
Work sampling also estimates delay allowances for time standards. If work sampling shows that operators spend 5 percent of their time waiting for materials, the delay allowance for time standards should include this 5 percent.
Advantages and Limitations
Work sampling requires less analyst time than continuous observation. One analyst can observe multiple workers in a single tour. Observations can be spread over days or weeks to capture normal variation.
The limitation of work sampling is that it provides proportions, not detailed time data. It cannot identify the specific causes of delays or the sequence of activities within a work cycle. Work sampling is best used as a screening tool to identify areas needing more detailed study.
Frequently Asked Questions
Is time study still relevant in the age of automation? Yes. Even automated processes require standards for setup, loading, unloading, and maintenance. Time study of manual elements within automated systems identifies improvement opportunities. As automation handles repetitive tasks, the remaining manual work becomes more skilled and variable — requiring better measurement, not less.
How do you handle operator resistance to time studies? Operator resistance is common and must be addressed through communication and trust-building. Explain the purpose — improving methods, not cutting rates. Involve operators in the analysis. Guarantee that time studies will not be used to reduce pay. Share the results and give credit for improvement ideas.
What is the difference between normal time and standard time? Normal time is the time a qualified operator takes to perform a task at normal pace. Standard time adds allowances for personal needs, fatigue, and delays. Standard time is the time allowed for the task — the basis for production standards and labor planning.
Can time and motion studies be applied to knowledge work? The traditional approach is less applicable, but the underlying principles still apply. Methods analysis reduces wasted steps in knowledge processes. Standard data for common tasks like data entry or report generation enables workload planning. The challenge is that knowledge work is more variable and less observable.
Work Design and Ergonomics — Ergonomics and Human Factors — Manufacturing Planning