As you depart on the outbound leg of a solo cross-country, it's reassuring to know that your request for traffic advisories has been approved by the local radar approach/departure facility. Now a controller will be pointing out inbound and outbound aircraft in the busy transitional airspace and beyond.
Experience has taught you that the aircraft you spot from the cockpit make up a small percentage of all that may be flying nearby. So it is always a relief when ATC advises that previously called traffic is “no longer a factor.” (Traffic that is “no longer observed” may still be flying nearby, however.)
Being seen by ATC when receiving advisories is why some pilots—nowadays those flying aircraft not equipped with Automatic Dependent Surveillance-Broadcast In (ADS-B In) technology—point to the service as a reason not to file a VFR flight plan. But understanding that limitations of radar advisories make it a less-than-perfect substitute should cause you to evaluate your options on a case-by-case basis.
For example, traffic advisories, which are discussed in the Aeronautical Information Manual and the Pilot/Controller Glossary, are issued “to the extent possible depending on higher priority duties of the controller or other limitations; e.g., radar limitations, volume of traffic, frequency congestion, or controller workload.” Also remember that advisories “do not relieve the pilot of his/her responsibility to see and avoid other aircraft.”
Also, just as you have learned that there may be more traffic out there than meets your scanning eyes, pilots are cautioned that “when a pilot requests or is receiving traffic advisories, he/she should not assume that all traffic will be issued.”
The nature of your flight also can have a large effect on the service you can receive. If you will cruise at a low altitude, terrain features or distance from the radar site may prevent receiving the same service as that available at higher altitudes, resulting in ATC advising, “Radar service terminated, squawk 1200.”
If your destination airport is situated in such an area, a considerable portion of your arrival and homeward departure phases will take place in a nonradar environment—a consideration to weigh carefully as you plan your flight.