You have to go back to the original sub-division plans (you will find them at the registry of deeds), and see precisely what rights were passed on from the previous owners to the developers.

The 'field' and your subdivision were likely owned by the same person at one time, and so rights of way between the two pieces may well be reciprocal. I rather doubt that the easement has to be 60' wide to be paved. I live in a similar subdivision that was laid out over 100 yrs ago, has developed and undeveloped 'private' roads, public 'rights of way' to bodies of water, a divested developer, etc. It's extremely complicated and gray, nothing is certain unless it has been land-courted - at least in this state. I also have a corner lot abutting an undeveloped and partially undeveloped right-of-way making my lot effectively twice as large as denoted in the plan. How much control I legally have over these areas is highly nebulous.

If you are serious, hire a lawyer VERY well-versed in these matters for your state.