A sign posted inside the bus shelter on 7th Street and Bryant Avenue N. in Minneapolis tells D Line riders that service will be so frequent that "you won't need a schedule."

Last week, Metro Transit rolled out a new operating plan on the D Line that aims to have buses arriving at stops at regular intervals rather than adhering to a schedule and trying to arrive at a specific time.

The idea is called "headway scheduling" and it's being employed on the rapid bus line running from the Mall of America in Bloomington to the Brooklyn Center Transit Station. Between 10 a.m. and 10 p.m. weekdays, the goal is to have buses consistently arrive at a stop every 10 to 15 minutes depending on the time of day, said agency spokesman Drew Kerr.

Headway is defined as the amount of time between two vehicles on the same route. On the D Line, Metro Transit's longest route at 18 miles, buses can struggle to remain evenly spaced out. Congestion, traffic signals, crashes, weather or a driver loading a passenger using a wheelchair can result in a bus falling behind schedule. Meanwhile, the bus behind may not encounter those obstacles and catch up to the one in front of it, resulting in two buses arriving at the same stop at the same time.

Known as "bus bunching," it results in some buses being packed while others have few passengers. Bunching also leaves big gaps between trips, leading to unpredictable service.

Onboard computers will tell D Line drivers when to begin a trip. The computer will tell the driver how close or far the bus is from the one in front of it. When bunching appears imminent, the operator can adjust as needed, such as holding at a stop to allow the bus in front of it get farther ahead. When there is enough room between them, the driver can resume the trip.

"The goal of headway scheduling is to have buses arriving at bus stops at evenly spaced intervals, improving service, reducing wait times and overcrowding," Kerr said. And it ensures operators have built in time to use the restroom, stretch and eat between trips, he said.

Printed schedules won't disappear as they still support trip planning and real-time information tools, Kerr said. But riders can expect buses to be more consistent.

D Line buses have an on-time rate of 75%, which means they arrive at a stop between 1 minute early and 5 minutes late, the agency said. While testing headway scheduling, Metro Transit will have buses on standby to ensure consistent arrivals, and deploy them should buses already on the route get too far behind, Kerr said.

Metro Transit has used headway scheduling on the A Line during the State Fair for the past two years. The A Line is a rapid bus line running from south Minneapolis to Rosedale Center and follows Snelling Avenue, a corridor rife with congestion during the fair.

Spacing out buses worked, "significantly reducing wait times," Kerr said.

Kerr said Metro Transit will evaluate D Line performance and collect customer feedback during the test before deciding how to move forward.