I would not use a single field formatted with a group of check boxes for this. The multiple selected values are stored as text with each value separated by a return character. This will make working with this data complicated.
Using a portal to a related table with one record per toll road would be a lot simpler.
Here's how you would verify that "Turnpike 87" was a selected check box:
not isempty ( filterValues ( yourtable::checkboxfield ; "Turnpike 87" ) )