On June 1, 2025, MSZT withdrew the MSZ EN ISO 13855:2011 standard. It was replaced by MSZ EN ISO 13855:2025. This is a significant professional change in the field of separation distance and stop time measurement.

Meanwhile, the legal environment is not entirely clear: the 2011 edition continues to be harmonized with the 2006/42/EC Machinery Directive. Manufacturers can legitimately refer to it, even though it has been withdrawn in Hungary. It is precisely this duality that makes professional responsibility all the more important.

What has actually changed?

The new edition modifies several basic concepts and calculation logic.

“Minimum distance” has been replaced by “Separation distance,” and “Overall System Stopping Performance” has been replaced by “Overall System Response Time.” The concept of effective detection capability (de) has also been introduced, drawing attention to the fact that physical detection capability and actual settings may differ, which directly affects the calculation.

Specific technical changes

– New calculation formula for perpendicular approach between 40–55 mm resolution

– For parallel approach, the formula C = 1200 – (0.4 × H) has been discontinued → DDS is now fixed at 1200 mm

– For two-hand starters, DDS = 550 mm instead of the previous C = 250 mm

– The maximum height of the lower protective radius has been reduced from 300 mm to 200 mm in general

– New calculation for determining the clearance underneath

– The possibility of undetected rear access must be examined

– The cold or warm state of the machine must be taken into account

After static separation distance, the way is now open for future protective devices (dynamic separation distance)

In practice, this means that many designs that were previously considered adequate may now result in insufficient separation distance.

A new approach to measuring stop-time

The new standard does not allow for simplification. A single measurement is not sufficient. A minimum of 10 measurements are required under all test conditions, and the average value does not count. A statistical method must be used to determine 99.7% coverage:

the higher of the maximum measured value or the average + 3 standard deviations must be taken into account.

Removing extreme deviations is not recommended, unless a measurement error can be proven.

The complete formula:

S = (K × T) + DDS + additional factors

Where:

– K = approach speed (1600 or 2000 mm/s)

– T = total system response time

– DDS = detection distance (the largest of DDO (overlap), DDT (crossing), and DDU (underlap))

– ZG, ZR, ZF, ZB, etc. = additional factors

This is no longer a simple “stop time measurement,” but rather leans toward complex system evaluation.

What does this mean in practice?

For machine manufacturers:

Previously validated designs may need to be recalculated.

For operators:

Periodic audits may reveal discrepancies that have not been apparent until now.

For two-hand controls:

The previously accepted distance of 250 mm is no longer sufficient in most cases.

ODRADE’s approach

At ODRADE, we base our stop time measurement procedure entirely on the EN ISO 13855:2025 standard.

We apply stricter or equivalent requirements to ensure full compliance.

We work with statistical-based evaluation. We take into account the approach method, effective detection capability, under/over/overlap possibilities, and all relevant additional factors.

Because safety distance is not just a number, but the last physical bastion of risk reduction.

If you are unsure whether your current measurements are correct according to the logic of the new standard, it is worth reviewing your system.

Safety cannot be based on old calculations, contact us today!