49 C.F.R. § B to Part 246
(1) The purpose of this appendix is to provide greater guidance on the procedures that should be employed in administering the vision and hearing requirements of §§ 246.117 and 246.118.
(2) For any examination performed to determine whether a person meets the visual acuity requirements in § 246.117, it is recommended that such examination be performed by a licensed optometrist or a technician who reports to a licensed optometrist. It is also recommended that any test conducted pursuant to § 246.117 be performed according to any directions supplied by the test's manufacturer and any ANSI standards that are applicable.
(3) For any examination performed to determine whether a person meets the hearing acuity requirements in § 246.118, it is recommended that such examination be performed by a licensed or certified audiologist or a technician who reports to a licensed or certified audiologist. It is also recommended that any test conducted pursuant to § 246.118 be performed according to any directions supplied by the test's manufacturer and any ANSI standards that are applicable.
(4) In determining whether a person has the visual acuity that meets or exceeds the requirements of this part, the following testing protocols are deemed acceptable testing methods for determining whether a person has the ability to recognize and distinguish among the colors used as signals in the railroad industry. The acceptable test methods are shown in the left hand column and the criteria that should be employed to determine whether a person has failed the particular testing protocol are shown in the right hand column.
Table 1 to Appendix B to Part 246
| Accepted tests | Failure criteria |
| Pseudoisochromatic Plate Tests | |
| American Optical Company 1965 | 5 or more errors on plates 1-15. |
| AOC-Hardy-Rand-Ritter plates-second edition | Any error on plates 1-6 (plates 1-4 are for demonstration-test plate 1 is actually plate 5 in book). |
| Dvorine-Second edition | 3 or more errors on plates 1-15. |
| Ishihara (14 plate) | 2 or more errors on plates 1-11. |
| Ishihara (16 plate) | 2 or more errors on plates 1-8. |
| Ishihara (24 plate) | 3 or more errors on plates 1-15. |
| Ishihara (38 plate) | 4 or more errors on plates 1-21. |
| Richmond Plates 1983 | 5 or more errors on plates 1-15. |
| Multifunction Vision Tester | |
| Keystone Orthoscope | Any error. |
| OPTEC 2000 | Any error. |
| Titmus Vision Tester | Any error. |
| Titmus II Vision Tester | Any error. |
(5) In administering any of these protocols, the person conducting the examination should be aware that railroad signals do not always occur in the same sequence and that "yellow signals" do not always appear to be the same. It is not acceptable to use "yarn" or other materials to conduct a simple test to determine whether the certification candidate has the requisite vision. No person shall be allowed to wear chromatic lenses during an initial test of the person's color vision; the initial test is one conducted in accordance with one of the accepted tests in the chart and § 246.117(c)(3).
(6) An examinee who fails to meet the criteria in the chart may be further evaluated as determined by the railroad's medical examiner. Ophthalmologic referral, field testing, or other practical color testing may be utilized depending on the experience of the examinee. The railroad's medical examiner will review all pertinent information and, under some circumstances, may restrict an examinee who does not meet the criteria for serving as a certified signal employee. The intent of §§ 246.117(d) and 246.118(d) is not to provide an examinee with the right to make an infinite number of requests for further evaluation, but to provide an examinee with at least one opportunity to prove that a hearing or vision test failure does not mean the examinee cannot safely perform as a certified signal employee. Appropriate further medical evaluation could include providing another approved scientific screening test or a field test. All railroads should retain the discretion to limit the number of retests that an examinee can request, but any cap placed on the number of retests should not limit retesting when changed circumstances would make such retesting appropriate. Changed circumstances would most likely occur if the examinee's medical condition has improved in some way or if technology has advanced to the extent that it arguably could compensate for a hearing or vision deficiency.
(7) Certified signal employees who wear contact lenses should have good tolerance to the lenses and should be instructed to have a pair of corrective glasses available when on duty.
49 C.F.R. §B to Part 246