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RSSB GOGGN3655 appendix B.2.1
My colour vision with regard to red and green meets the requirements (IE, normal vision). The test that is used does not show this. Ergo the test is not appropriate.
The problem is, the RSSB is scared to change the recommendations and TOCs are afraid to use something different because of cost/change/potential incidents I guess. In the case of potential incidents, they should not employ people who eat a lot of red meat as that could cause health problems too!
If you go a bit further down the quoted document
B.2.4 Colour vision tests need to be easy to administer while giving accurate and reproducible results. The Ishihara Test meets these requirements and is very sensitive for detecting red-green abnormalities
and if you look at the reference material
www.hse.gov.uk/pubns/WEB0.pdf
24 Employers must decide whether a person with a slight defect is acceptable for the colour tasks they are required to perform and chose the test accordingly. Subjects who pass the City University test but fail the Ishihara plate test are likely to have practical difficulties with only the most demanding colour discrimination tasks in an occupational context, such as situations involving colour recognition of transport signals. In these cases lantern and trade tests can be used to determine suitability.
Then there is this taken from GO/RT3451
Normal colour vision:
use of a recognised test, such as Ishihara, as well as another recognised test if required, Individuals who pass a properly conducted Ishihara test can be considered to have normal colour vision for the purposes of this requirement. The recognised doctor may also use other validated tests of colour vision at their discretion, for example if acquired colour vision deficiency is suspected.
A.1.28
Different tests may not be equivalent when measuring the same aspect of colour vision. Therefore, some individuals may be able to pass one test but not another and this has important implications for interoperability and for the employee that wishes to change their employer or job.
A.1.29
Advice on other validated tests of colour vision can be found in RSSB’s final research report T940 Identification of a robust colour-vision testing protocol for the rail industry.
And then there is the Train Driver Licenses and Certificates Regulations 2010
Schedule 1 (2) Vision
e)normal colour vision: use of a recognised test, such as Ishihara, as well as another recognised test if required,
Finally to LUL. They only use an alternative in certain circumstances.
Taken from LUL Document S1604 Vision Standard for Personnel Requiring Safety on the Track Certification
3.5.6 For LU employees only, the LU Category 5 Standard (S5606 – Colour Vision Standard) applies. For all other personnel colour vision shall be tested using the Ishihara test. .
And then LUL S5605.
3 Requirements
3.1 Colour vision requirements
Note: This standard must be read with LU Category 1 Standard S1604 Vision standard for LU staff who require safety on the track certification.
3.1.2 Colour vision for TfL staff shall be assessed by the red and green safety critical colour vision (threshold) requirements.
3.1.3 Colour vision must meet the colour assessment and diagnosis thresholds defined in this standard.
3.2 Colour vision test
3.2.1 The colour assessment and diagnosis test shall be applied using the following standard Normal (SN) unit thresholds, determined by TfL OH: Deutan < 7 SN Protan < 10 SN
So it seems that Ishihara is here to stay as the go to colour vision test for the rail industry. Using a comparison between pilots and train drivers cannot really be made for medical fitness standards as each industry presents its own issues.
