As pointed out in the section "PTC Analyses," “validation and verification” is a key requirement as part of a Product Safety Plan (PSP). Validation involves several analyses that have been outlined in that section; verification involves data collection, performance evaluation and product refinement. The results of this process are also expected to be included in the PSP submitted to FRA for approval.

The testing is usually comprised of several steps:

Step 1 - Subsystem Testing

Each unit of the whole system is first tested by itself. This is to verify that the subsystem unit is designed and built correctly. The unit's software code is also checked to detect any deficiency. 

Step 2 - Laboratory Integration Testing

The subsystems units are assembled into one system to verify the adherence of the system functionalities and design to the requirements in a laboratory setting before subjecting the system to operation in the field. Requirements are first analyzed to design a comprehensive matrix of operational scenarios. Where a segment (such as a locomotive or train) cannot be physically housed in the laboratory, it will be simulated. A simulation model containing a real locomotive cab with a throttle and brake can be used to interact with other segments of the system. The dispatching system is usually also simulated in this environment. After the system passes the tests in this laboratory environment, there should be a confidence that most requirements, if not all, are met and that the system should function as it is intended in all aspects.

Step 3 - Field Testing

Upon successful laboratory test, the system can be put into testing in an actual railroad environment. A lot of the laboratory testing will be repeated in this field test since the system will interact with actual infrastructure, which is not as controlled and predictable as in the laboratory environment. Some tests are repeated in various locations and various times so that the randomness and variability can be also tested. Certain testing, such as actual train tracking with GPS and an inertial navigation system, can only be performed in the field. At this time, certain train operation is still in a control environment. Speed may be controlled to check the braking distance or the activation of alarms. Train orders may be artificially created for verifying the correct receipt and response in the controlling locomotive. Upon successful field testing, FRA may grant approval to elevate to the next level of testing: revenue service. 

Step 4 - Revenue Service Testing

In this final phase, the system is cut-in in actual railroad operation, after proper notification and training. Initially, even though technical and managerial personnel are not on board the locomotives or trains, system monitoring is still intense at the beginning and will be eased off as confidence is built. Quite often, the monitoring is performed remotely in shadow operation. The crew is specifically instructed to follow the existing method of operation. The enforcement function of the PTC system is not cut-in, but the system operation performs as if the trains are operated under PTC operation. The wireless communication network, the interaction among segments, system malfunctions and faults, and general operational difficulties can be revealed and logged in a central office. The system is continuously debugged and refined in this process. The enforcement function will then be turned on when no hazard is revealed after a certain monitoring period. The crew is instructed to operate the trains under the PTC method of operation. It is not unusual for this phase to last 6 months to 1 year before complete confidence is built for the successful deployment.