Headway 101

What is Headway?

Headway is the amount of time between transit vehicles on the same route. The more headway between vehicles, the longer passengers have to wait at a stop if they miss the first vehicle

The schedule published by a transit agency defines the scheduled headway, or frequency, of vehicles on a route. A schedule may specify, for instance, that a bus or train car should arrive every 10 minutes. But vehicles don’t always achieve their scheduled headway because of congestion and other real-life variables.

Uneven headways create a poor rider experience. A rider waiting at a stop may see two vehicles go by back-to-back then wait for an extended period of time, just to sit on the next vehicle, which might be overcrowded because it has to pick up more passengers. Additionally, as headways start to get off schedule, the problem tends to get worse. 

How does Swiftly Show Headway?  

Swiftly shows headway deviation, which is the difference between the actual headway and the scheduled headway.

There are three statuses for headway deviation:

• Expected: When actual headway matches scheduled headway. 
• Bunched: When actual headway is less than scheduled headway; vehicles that are too close together. 
• Gapped: When actual headway is greater than scheduled headway; vehicles that are too far apart.

How does Swiftly Calculate Headway?

In Swiftly, a vehicle’s headway is measured by comparing its predicted arrival time at the next stop with the arrival time of its leader (the vehicle just in front on the same trip pattern).

By default, a vehicle will be considered bunched if the actual headway is 75% or less than the scheduled headway. A vehicle will be considered gapped if the actual headway is 125% or more than the scheduled headway. 

For example:

• If your scheduled headway is 20 minutes, then vehicles can be at minimum 15 minutes apart and at maximum 25 minutes apart to be considered within expected headway. 
• If two vehicles on the same route are less than 15 minutes apart, the headway status would be bunched for the trailing vehicle. 
• If two vehicles on the same route are more than 25 minutes apart, the headway status would be gapped for the trailing vehicle. 

Swiftly calculates the headway status of a vehicle for historical insights, in our Headway Insights product, GPS Playback, and in our real-time product--Live Operations.

Historical Insights

For historical insights, Swiftly calculates the headway status of a vehicle at the departure of each stop along a route. The default headway rules are configurable.

Real-Time Data 

For real-time data, Swiftly calculates the headway status of a vehicle based on the real-time vehicle locations in comparison to the vehicle in front of it. 

Tip: These defaults can be modified by your agency upon request. Please contact [e-mail].