I have been searching through old Electric Railway Journals as well as the New Haven Railroad Historical & Technical Association's magazine "Shoreliner". I did find some information in the "Trolley Stop" series of articles in the Shoreliner volume 19, issue 3 stating that the trolley RPO routes in New Bedford were as follows:
Providence, Rhode Island and Fall River, Massachusetts from 1902-1924
Providence, Rhode Island and New Bedford, Massachusetts from 1929 -1930
Providence, Rhode Island and Fall River, Massachusetts from 1930-1932
Unfortunately that was about all I could discover on the RPO routes. In a later issue of the Shoreliner I was able to discover why 302 was numbered in the 300 series, as was all of Union Street Railway's freight equipment. In Volume 20 Issue number 3 the Trolley Stop article written by the late Charles Brown, describes the formation of the "Electric Express Company". The company was formed by the New Haven Railroad as a result of the ban placed on the railroad by the state of Massachusetts preventing direct ownership of any electric railways in the state. The function of the Electric Express Co. was similar to that of the Railway Express Agency for the steam roads. All freight motors used were very similar in appearance, but not identical. Most of the traction companies were owned by the New England Investment & Security Company, and some were independent. It should be noted that the New England Investment & Security Company was in turn owned by the New Haven Railroad. In order to identify ownership of the freight motors, all companies involved utilized a specific number series as shown below:
Bay State Street Electric Railway - car numbers 1 thru 44
Milford, Attleboro & Woonsocket - 0100 series
Worcester Consolidated Railway - 0200 series
Union Street Railway - 300 series
Springfield Street Railway - 0400 series
Boston & Worcester Street Railway - 500 series
Berkshire Street Railway - 0600 series
All traction lines with the exception of the Bay State, Union St Railway and the Boston & Worcester were owned by the New England Investment & Security Company. As 302 was originally built as a freight trailer as seen in the photo posted earlier, now we know how 302 got its number.
If any of the readers has any contradictory information I'd be glad to post it on here as my goal is to get the information correct. Feel free to drop me an Email at fullparallel@cox.net
Till next time......