General Order 64-A
Supply Lines And Communication Lines Crossings Over Railways
114.1 Additional Insulation.
Where grounded pins are used at crossings (non-grounded construction being used at other parts of the line), the insulators used on such metal or grounded supports shall have a ratings of 25% greater than the flash-over voltage values of the line insulators except where these values exceed those specified in Table 9, Rule 55.3, by 50%. As an alternative, the conductors at their points of attachment, where suspension insulators are used, may be protected by arcing shields.