Steamship Authority governors are scheduled to vote on a set of sweeping rate hikes at their meeting Tuesday — the second substantial rate hike in as many years for the ferry line.

The meeting begins at 9:30 Tuesday and is open to the public via Zoom.

Part of the $112 million 2021 operating budget, the across-the-board rate hikes include a $15 one-way increase to peak summer vehicle pricing on the Vineyard route, along with slightly smaller increases in off-season and excursion fares and the first passenger fare hike since 2015.

Governors are expected to approve the rate hikes in a year when passenger traffic has seen a substantial drop due to the pandemic.

Since its inception in 1960 and until this year, the boat line has operated comfortably without state and federal subsidy — only incurring an operating deficit a handful of times. It is one of the only transportation services in the country that operates from the fare box.

The boat line charter allows the state to tax port communities if it runs a deficit.

But this year, with traffic plummeting in the spring and early summer due to the pandemic, a one-time state budget amendment was passed by legislators and signed by the governor that shifts the burden of any deficit — currently projected at around $10 million — onto the commonwealth.

Using data provided by the SSA, a look back at the 30-year history of fare hikes shows that rates for both passengers and vehicles have been steadily climbing since 1990 — generally outpacing the rate of inflation. The recent fare hikes mark the most substantial price increases over the past three decades, particularly for summer automobile pricing. Peak-period pricing is a new practice adopted for the first time last year.

Fare structures have changed over the years too, including for commercial vehicles.

According to the data, one-way passenger fares have doubled over the past three decades, increasing from $4 to $8. One-way passenger fares were $5 in 2000, $6 in 2006, $7 in 2010 and $8 in 2015.

The proposed passenger rate hike this year, the first since 2015, would increase passenger fares to $9 per one-way trip.

Automobile pricing has increased more substantially over the past three decades, tripling since 1990, when the one-way summer vehicle price was $30. The price is now between $90 and $110 depending on vehicle size and the day of travel.

Off-season, one-way vehicle fares have also more than tripled since 1990, increasing from $15.25 to either $55 or $65 depending on vehicle size.

According to the U.S. Bureau of Labor Statistics, the value of $1 in 1990 has the same buying power as $2.04 in 2020, meaning boat line automobile prices have more than tripled while the rate of inflation has doubled.

The largest increase in automobile pricing came in 2019, when the boat line instituted a $12.50 fare increase to one-way summer car fares, raising the cost from $68.50 to $81. That price increase was followed by a $4 increase in 2020, and a proposed $4 to $6 increase in 2021, depending on vehicle size.

The proposed $20.50 rate hikes over the past three years followed a 17-year period between 2000 and 2017 in which vehicle pricing only increased by $19.50, with no summer vehicle price increase between 2013 and 2018.

Rate increases were adopted in 2019 and 2020 to pay for changes outlined in a consultant’s report critical of the ferry’s operations. The report suggested greater focus on vessel maintenance and the hiring of certain administrative and front line staff.

The 2020 rate hike also included an $11.50 off-season automobile fare increase, raising the price from $43.50 to $55 between November and March, as well as a $5 round-trip increase in excursion fares — deeply discounted round-trip car fares intended for year-round Islanders.

Excursion fares have also more than tripled since 1990, with summer prices rising from $30 round trip to $99. The 2021 fare increases include a $5 to $7 round-trip price hike for excursion vehicles.

Although the SSA has long engaged in price differentiation, with off-season vehicle fares generally about half the summer fares, last year marked the first time that the boat line had instituted peak travel prices for weekend summer vehicle trips — a practice that will continue this year.

The 2021 rate increase raises the one-way peak summer vehicle fare from $100 to $115 for vehicles traveling between Friday and Sunday. Last year when the practice was introduced, the price of a peak one-way summer car fare increased from $81 to $100.

The rate hikes will also include increases for parking and commuter booklets.

Similar price increases have occurred for truck fares, which have gone up from $62.40 in 1990 to $157.00 in 2020.