Three regional cost-sharing agreements account for the lion’s share of fiscal business coming before West Tisbury voters at a special town meeting Tuesday.

The meeting begins at 7 p.m. in the West Tisbury School gymnasium. Moderator Daniel Waters will preside. There are seven articles on the warrant.

The most complex is a warrant article which proposes changing the assessment formula for TriTown Ambulance from an even split to an allocation based in part on call volume in each of the three up-Island towns.

The new formula, assessing 25 per cent of the ambulance service’s expenses and revenue according to call volume while the remaining 75 per cent continues to be shared equally, was approved by the Chilmark and Aquinnah select boards at a three-way meeting of town leaders earlier this fall.

Saying the new formula would affect their town’s taxpayers the most, West Tisbury board members voted instead to bring the new formula to a town meeting. The finance and advisory committee subsequently voted 4-1 to not recommend the article.

The biggest ticket on Tuesday’s warrant is a request for $257,370 to put toward the West Tisbury School roof project, which is nearly $322,000 short of its latest $644,000 estimate.

The article hinges on a vote by the other two up-Island towns to pay their share of the increased estimate.

Another article, an agreement to repay the town of Chilmark for West Tisbury’s share of a $950,000 borrowing measure for the Chilmark School heating and ventilation system, also requires approval from all three towns.

Chilmark voters, who are responsible for 80 per cent of the cost of work at the school, agreed to the inter-municipal pact at their special town meeting last Saturday.

A request for $5,000 would go toward the Martha’s Vineyard Commission’s storm tide pathways mapping project.

The first article on the warrant, submitted by town clerk Tara Whiting-Wells, asks that Saturdays be officially designated holidays for the purpose of business in her office, meaning they will not be counted as business days for purposes of submitting papers or filing other papers with the clerk.

Veterans and residents over 60 will be able to offset their property taxes by performing up to 125 hours of volunteer work for the town, if voters approve two articles which are based on provisions in state general law.