San Diego runs on a single regional fare system that covers nearly everything — tap once and the same card works on city buses, the Trolley, and the commuter trains up the coast. Fares are cheap, and a direct bus gets you from the airport into downtown in a quarter hour.
The basics
The San Diego Trolley, run by MTS, is the backbone: four light-rail lines meeting downtown and radiating out from there.
- UC San Diego Blue Line — the busiest line, running from the Mexican border at San Ysidro up through downtown to the UC San Diego campus and the Westfield UTC mall.
- Orange Line — downtown east to El Cajon Transit Center.
- Green Line — downtown through Mission Valley and SDSU out to El Cajon Transit Center.
- Copper Line — the newest line (opened 2024), a short connector between El Cajon Transit Center and Santee.
Around the Trolley, MTS runs the city’s buses, including faster limited-stop Rapid routes. North of the city, a separate agency, North County Transit District (NCTD), runs the COASTER commuter train (Oceanside to downtown San Diego), the SPRINTER hybrid rail line (Oceanside to Escondido), and BREEZE local buses — useful if you’re headed to Carlsbad, Encinitas, or Legoland.
How to pay
San Diego’s fare system is called PRONTO, and there are three easy ways to pay:
- Tap a contactless bank card or your phone (Apple Pay / Google Pay) at any PRONTO validator. It charges the $2.50 adult fare — simple, but it only ever charges the adult rate and doesn’t build toward a day or monthly cap.
- Get a PRONTO card (one-time $2 fee, at station machines, the MTS Transit Store, or retail outlets) or use the PRONTO app, load money on, and tap to ride. This is the way to go for reduced fares, and the only way to get automatic fare capping.
- Pay cash on the bus or at rail station machines — but cash rides don’t include free transfers.
Tap the validator before you board, every time — including transfers. Inspectors do check for proof of payment, and since February 2025 they issue a citation directly rather than letting you buy a fare after the fact.
Fares
A single tap buys 2 hours of unlimited transfers across MTS bus and Trolley:
| One-way fare | Day pass | Monthly pass | |
|---|---|---|---|
| Adult | $2.50 | $6.00 | $72 |
| Senior / Disabled / Medicare / Youth | $1.25 | $3.00 | $23 |
If you’re using a PRONTO card or the PRONTO app, you get automatic fare capping: once your taps in a day add up to the day-pass price, the rest of that day is free, and the same happens at the monthly-pass level across a calendar month. You don’t need to buy a pass up front — just keep tapping the same card.
Premium Rapid Express routes (280, 290) cost more ($5.00 adult one-way), and rural routes cost more still ($8.00 adult one-way).
Getting from the airport
San Diego International Airport (SAN) isn’t on the Trolley, but a direct bus makes the trip easy:
- Route 992 (Airport/Downtown Shuttle) stops at both terminals and runs to Santa Fe Depot downtown, where you can connect to all three original Trolley lines, Rapid buses, the COASTER, and Amtrak.
- Cost: $2.50, same as any other MTS ride.
- Time: about 15 minutes to Santa Fe Depot.
- How often: every 15 minutes for most of the day, seven days a week.
If you’re headed straight to Old Town instead, the free San Diego Flyer shuttle connects the airport to Old Town Transit Center (first pickup around 4:45am, last around 12:30am) — but it’s for transit riders only, so you’ll still need to connect onward from there.
Apps to download
- PRONTO — the official app for loading fares, tapping to ride, fare capping, and trip planning with real-time arrivals.
- One Bus Away — a straightforward option for checking real-time bus and Trolley arrivals.
- Google Maps or Apple Maps — good for planning, with live MTS and NCTD data built in.
When it runs
- UC San Diego Blue Line: every 7.5–15 minutes, daily, from about 4am to after midnight.
- Green Line: every 15 minutes from about 5am to 11:30pm daily (last trip from El Cajon to downtown around midnight).
- Orange Line: every 15 minutes weekdays 4:30am–11pm (30-minute service to about midnight); similar frequencies on weekends, thinning to 30 minutes in the evening and early morning on Sundays.
- Copper Line: every 15 minutes for most of the day.
There’s no true 24-hour service on any line — plan around late-evening last trains.
Accessibility
Trolley stations and MTS buses have level or ramped boarding. MTS Access is the region’s ADA paratransit service for riders certified as functionally unable to use fixed-route transit — call MTS Access to confirm your trip falls within its service area, and get certified before booking a ride.
Etiquette & local quirks
- Tap every ride, even transfers — your tap is your proof of payment, and inspectors do check.
- Bikes ride the Trolley: up to two per car off-peak (one during peak hours) — you’ll need to stand and hold it. E-bikes with lead-acid batteries or gas-powered bikes aren’t allowed.
- No eating on board; drinks need a spill-proof or screw-top lid.
- Give up priority seating near the doors when asked — it’s enforceable, with fines starting at $25.
- Headphones are required if you’re playing audio out loud.
- Heading up the coast to Carlsbad, Encinitas, or Legoland? That’s NCTD territory (COASTER, SPRINTER, BREEZE) — a separate system, though PRONTO covers it too.
Good to know
- Fare enforcement changed in 2025: if an inspector catches you without proof of payment, you’re cited directly — there’s no more buying a fare after the fact. A citation resolved through the Diversion Program runs $25; let it lapse and it can become a much larger traffic-court fine.
- Fares are going up. MTS and NCTD monthly passes rise from $72 to $85 for adults (and $23 to $28 for senior/disabled/Medicare riders) later in 2026, with a further increase to $95/$30 in fall 2027 — a fare change recommended by MTS and NCTD and approved by the SANDAG Transportation Committee in July 2026 to help close a budget shortfall. A new low-income program, PRONTO LIFE, is set to launch October 1, 2026, freezing fares for riders enrolled in CalFresh, Medi-Cal, or CalWORKs. The one-way and day-pass fares quoted in this guide reflect pricing as of mid-2026 — check MTS’s site if you’re reading this well after that.