49 CFR Part 655.45(k) states:
In addition, there was guidance published in the Implementation Guidelines for Drug & Alcohol Regulations in Mass Transit (pgs. 2-4) that applies to contractors but also may be applied to municipalities/counties/etc. with FTA and FMCSA regulated employees commingled. This states:
Contractors Covered Under the Regulations of Other Modes. Many transit systems contract with safety-sensitive contractors who are already required to comply with the drug and alcohol testing regulations of other modes (i.e., FMCSA). If these contractors are able to segregate the employees who provide transit service from those who perform safety-sensitive functions for the other modes, the employer is required to establish programs for each group of employees allowing for the corresponding differences in the modal rules.
However, if the contractor's employees perform safety-sensitive functions for both transit and another mode, the employer must determine which modal administration regulates the majority (>50 percent) of the employees' who perform safety-sensitive functions covered under the USDOT. Once determined, the employee will be subject to pre-employment and random testing under the regulatory authority of the primary modal administration. The assignment of regulatory authority for reasonable suspicion and post-accident testing will depend on the function an employee is performing at the time of the incident/accident. Return-to-duty and follow-up tests will be assigned to the modal administration that generated the initial positive test result.
It is important for transit employers to remember that the only thing that has changed is that transit systems have the OPTION to lower their random drug testing to no less than 25%. This in no way means that any system has to change anything, and it is not a directive to lower the rate. The regulations require transit systems to set a random testing rate, and they will be compliant if they have any number over 25% for drugs.