It is one of the most frustrating experiences a transit rider will face: You arrive at the platform just in time to see the taillights of your train pulling away from the station, without you on board. You take a seat, resigned to the reality that a full 15 or 20 minutes will pass before the next train arrives.

This scene has become all too common in Atlanta. For decades now, we have seen a steady and relentless deterioration of service levels on our buses and trains. Take MARTA’s rail system: in the 1980s, trains ran every 6 minutes, a tolerable wait time for most riders. Since then, the wait time has gradually crept higher and higher: to 8 minutes in the 1990s, to 10 minutes in the early 2000s, and eventually to the 15-minute waits that riders must endure today.

The importance of frequency to a successful transit system cannot be overstated. Transit expert Jarrett Walker, author of the book “Human Transit,” has helped make “frequency is freedom” a catchphrase for transit planners. “Your car or bicycle is always ready to go when you are,” Walker explains. “Frequency is the measure of how close transit comes to that same freedom.”

By that measure, the freedom afforded by Atlanta’s transit system today is quite low, and that is increasingly putting the city at a competitive disadvantage. No comparable rapid transit system in the country makes its riders wait as long as we do here.

Local officials often point to budget shortfalls when explaining the current service levels. Of course, most of our peer cities have also been battling severe transit funding challenges, but they have found ways to economize that don’t require such drastic service cuts. There is an understanding in these places that frequent, reliable service is absolutely essential and must be prioritized.

Unfortunately, that message is often lost here, where service quality is typically the first thing to go when budgets become tight. This is true even of brand-new projects like the Atlanta streetcar, currently set to open with skeletal 15-minute service. While transit advocates are genuinely excited about the expansion of our rail system, there are legitimate concerns that excessive wait times could cripple the streetcar’s effectiveness from Day One.

While the current situation may be discouraging, viable options for improvement do exist. Even modest increases in capacity can yield dramatic improvement for riders. The streetcar, for example, could cut its wait time by a third by adding just one vehicle to the route. And MARTA could look to innovation in places like Europe and Asia, where metro systems are increasingly employing high-tech solutions such as fully automated trains to improve efficiency, and are seeing impressive results.

However we get there, one thing is clear: Atlanta’s transit system will continue to lag behind if quarter-hour wait times continue to be the standard. Frequency is freedom, and Atlanta must be willing to offer its transit riders that freedom if it is going to compete on the world stage.

David Emory is president of Citizens for Progressive Transit, a transit advocacy group.