In CT the Merritt Pkwy & Wilbur Cross Pkwy are not a big issue and the bridges are high enough. They prohibit commercial vehicles and vehicles over 7500 pounds and 8'... no mention of RVs on the signs. You should be OK... I use the parkways, as do many other vans.
In NY, anything with "parkway" in it's name is specifically called out as "no trucks" - only passenger cars. They allow some NY pickup trucks to get passenger plates and use the parkways, but no trucks, vans, or anything commercial is allowed. They do not recognize CT combination plates (for RVs) a passenger plate so they are a no-go. The bridges on some NY parkways are very low... I'd stay off NY "parkways" if your plates do no say passenger and/or if the size limits apply.
Depending on where you are on LI, you may choose to take the Port Jefferson - Bridgeport ferry to I-95 in CT. That is not cheap, but cuts out hours of driving through some pretty congested NY areas near NYC. They take vans... probably about $80, you'd can call them to get the details. With the price of gas, that may not be too bad... BeaR is OK !
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