Half of all Utah Transit Authority bus routes — 61 out of 121 — are changing this Sunday in one of the biggest “change days” ever for the agency.

Increased offerings — such as service until midnight on some key routes, and more Sunday operations — are coming from money that Salt Lake City is providing to enhance bus routes there, or from recent tax hikes for transit in other areas.

“This is just the beginning of the service improvement that we’re looking forward to making,” said Eric Callison, UTA manager of service planning.

Details of changes are available online at rideuta.com. Here is a look at some of the bigger ones:

Salt Lake City

Thanks to city funding from its Funding Our Future program tax hike, major improvements are being implemented on Routes 2 (mostly along 200 South to the University of Utah), 9 (along 900 South, now extended through Glendale and Poplar Grove to the University of Utah) and 21 (along 2100 South also to the U.).

“They are going to 15-minute service on weekdays and Saturdays, 30-minute service on Sundays, plus early-morning and late-night service” until midnight on weekdays and Saturdays, Callison said. “It is basically revamping those routes to a much higher level of service.”

Route 220 (which travels from Sandy to Salt Lake City) will also run along 200 South instead of 100 South, scheduled in such a way that between it and Route 2, buses will arrive about every seven to eight minutes on most of 200 South.

Also added is a new Route 4 from Poplar Grove to Olympus Cove via 400 South and Foothill Drive. It will provide service to downtown Salt Lake City and the University of Utah and will replace portions of Routes 228 and 516.

Callison said changes on Routes 4 and 9 now better connect the west and east sides of the city, and no longer require transfers to travel across it.

“We’re really increasing the amount of access that people on the west side of the city have and we’re very excited about that," he said. “Increasing hours, increasing frequency, just making it a lot more possible for people to use the transit system and get around without a car.”

Callison notes that some routing and schedule changes will occur on many bus routes in the city to allow for easier transfers and connection and future improvements envisioned by the city’s transportation master plan.

He also said that, at the request of the U. to ease traffic problems, most bus routes will no longer directly serve the hospital loop. Some buses that had waited there between beginning and ending routes will now wait at new spots being added in front of the school’s student union building.

Salt Lake County

While the county recently approved a tax hike for transit, increased bus service from that is not coming yet. Callison said the first major portion of service enhancements from that tax hike is expected later this year with a “microtransit” pilot program in the southwestern portion of the county.

It will be a hybrid between ride-hailing companies like Uber and Lyft and traditional service. Residents will be able to use smartphones or call a service center for a van to pick them up — and will be given an estimated time for pickup and arrival. It will charge traditional bus system fares. It will connect to other UTA services, or drop off at destinations in the area.

Salt Lake City is also nearing the launch of its own microtransit service.

Tooele County

Currently buses go from Tooele County to Salt Lake City only in the morning and evening. UTA is adding midday service, using money from the Proposition 1 tax hike that Tooele County residents approved in 2015.

UTA also is realigning routes to allow more service to Grantsville, which currently has only one trip a day. “We’re going to have five trips,” Callison said.

Weber County

Two new lines are being added using Prop 1 tax hikes that were also approved there.

The new Ogden Trolley, Route 601, will connect downtown Ogden with Washington Blvd. and the Ogden FrontRunner Station. “We will use the trolley-style buses that we use on a couple of other routes,” Callison said. It will run every 20 minutes on weekdays and Saturdays.

Also added is a new flex route, F620, that will connect Ogden and Roy FrontRunner stations to previously unserved areas in West Haven and West Ogden. “That’s just a new growing area," Callison said, “so we’re excited to be able to provide service to that part of the county.”

Utah County

UTA is discontinuing the once-popular Route 811, which connected Provo to the Blue Line TRAX in Sandy.

“Route 811 used to be a very busy route but since FrontRunner opened in 2012, ridership has steadily declined,” Callison said. “We are reallocating some of those resources to better serve the high-tech corridor and provide holiday service” in that area.

While the 811 ran only during rush hour, the replacement Route 871 will also offer midday service seven days a week.

“That is a good improvement for people who are trying to travel between Utah County and Salt Lake County but are not able to pay a premium fare” for FrontRunner service, Callison said.