Gates functionally form a dead-end if they aren't open to the public, and this gate appears to not be accessible by anyone, hence the culdesac for turning around. A road that can't be traveled from one end to the other by regular traffic 2/47 probably shouldn't be classified higher than unclassified or residential or else it's misleading, as secondary classification usually implies it's a busy commercial arterial road, connects to other major roads at each end, has something of significance like a village/town or airport at its terminus in the instance it is a dead-end road, or anything along the lines of those. 

Looking at the Bing Maps streetside imagery, there appears to have been a gate here for a while. My guess is that historically this road linked Flanders and Netcong but simply no longer does and just maintains the name, and that US 206 functionally serves as the bypass.

I should note that it is very common for dead-end roads, unpaved roads, or roads without lane markings throughout the US to have 40+ speed limits in rural scenarios, whether that speed limit may be a relic of when the road served as a major highway but is now a local road or is simply there because the road is lightly traveled. It's also very typical for roads that hit dead-ends like this one to retain their lane markings if they're functionally converted to local roads like in this situation. Not sure why, but I assume it has more to do with how the DOT maintains the road versus for any navigational purposes.