Machine Safety: Crossing the yellow line

Yellow line theory versus complacency: On a train platform few people cross the yellow line, without any specialized training, yet, in a manufacturing environment, accidents happen regularly after people cross the yellow line and even more formidable barriers. Why?


Why don’t more people heed the yellow line more often in a manufacturing setting? They do at the train station. Courtesy: Control EngineeringThe "yellow line" in manufacturing has been around for a very long time. But, a "yellow line" is frequently tested in manufacturing versus the "yellow line" on a train platform. Do people understand the "yellow line" theory differently? Both carry high potential hazard levels.

Many of us have stood on a busy train platform and witnessed crowds conforming to standing behind the yellow line (or out of the yellow zone) along the platform, where trains pull in for people to disembark from and board the train. Typically there are no signs, roving police, training, or regulations governing these high-risk areas. The crowds of people are often distracted by children, phones, newspapers, conversations, and occasionally rushing to catch a scheduled train. Yet, very few incidents occur. Let's face it: Those who do accidentally fall over the yellow line into an oncoming train have likely purchased their last tickets. 

Compensation theory

Is this a human risk compensation theory suggesting that people typically adjust their behavior in response to the perceived level of risk?

Industry (in my opinion) has a whole different approach to the "yellow line" theory. I believe that potential known hazards in manufacturing facilities are identified in different ways, primarily via regulations, codes, standards, and company policy. Yellow lines are one way hazards are designated in industry.

Hazards behind the yellow lines in industry are perceived differently than on a train platform. For example, people have jobs running machinery behind the yellow lines along walkways and aisles in manufacturing facilities. Some people are prohibited from crossing these yellow lines, and others are permitted. Those permitted must have special training, in some cases have special personal protective equipment (PPE) protection, and in most cases be an employee with special authorization. Yet, many more incidents occur in comparison to the train platform. [subhead]

Possible answer

Perhaps this human risk compensation theory suggests that people typically adjust behavior (complacency) in response to the perceived level of risk accompanied with frequency of exposure.

These very different characteristics of human behavior need to be considered when setting safety policies. See questions below and post your comments below.

- J.B. Titus, Certified Functional Safety Expert (CFSE), writes the Control Engineering Machine Safety Blog. Edited by Mark T. Hoske, content manager, Control Engineering,


Editor questions

1) If penalties were more severe in the workplace, would there be fewer accidents? That is, if employees knew that crossing the yellow line once meant they have punched their last time clock for that employer, would that reduce risk?

2) Do employees know what infractions, would result in dismissal?

3) Safety policies; safety markings, signs, and guards; and safety technologies: The greatest of these is...?

Reply in the comments section below. has related machine safety explanations.


ASSE — Professional Safety Journal- Near-Miss Reporting, May 2013

OSHA — search for near miss

Contact: for "Solutions for Machine Safety."

- See related articles on safety culture below.

No comments
The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by...
The System Integrator Giants program lists the top 100 system integrators among companies listed in CFE Media's Global System Integrator Database.
Each year, a panel of Control Engineering and Plant Engineering editors and industry expert judges select the System Integrator of the Year Award winners in three categories.
This eGuide illustrates solutions, applications and benefits of machine vision systems.
Learn how to increase device reliability in harsh environments and decrease unplanned system downtime.
This eGuide contains a series of articles and videos that considers theoretical and practical; immediate needs and a look into the future.
Additive manufacturing benefits; HMI and sensor tips; System integrator advice; Innovations from the industry
Robotic safety, collaboration, standards; DCS migration tips; IT/OT convergence; 2017 Control Engineering Salary and Career Survey
Integrated mobility; Artificial intelligence; Predictive motion control; Sensors and control system inputs; Asset Management; Cybersecurity
Featured articles highlight technologies that enable the Industrial Internet of Things, IIoT-related products and strategies to get data more easily to the user.
This article collection contains several articles on how automation and controls are helping human-machine interface (HMI) hardware and software advance.
This digital report will explore several aspects of how IIoT will transform manufacturing in the coming years.

Find and connect with the most suitable service provider for your unique application. Start searching the Global System Integrator Database Now!

Infrastructure for natural gas expansion; Artificial lift methods; Disruptive technology and fugitive gas emissions
Mobility as the means to offshore innovation; Preventing another Deepwater Horizon; ROVs as subsea robots; SCADA and the radio spectrum
Future of oil and gas projects; Reservoir models; The importance of SCADA to oil and gas
Automation Engineer; Wood Group
System Integrator; Cross Integrated Systems Group
Jose S. Vasquez, Jr.
Fire & Life Safety Engineer; Technip USA Inc.
This course focuses on climate analysis, appropriateness of cooling system selection, and combining cooling systems.
This course will help identify and reveal electrical hazards and identify the solutions to implementing and maintaining a safe work environment.
This course explains how maintaining power and communication systems through emergency power-generation systems is critical.
click me