The use of 155.370, caught on in Michigan after the tragic 1965, Palm Sunday Tornado Outbreak that caused considerable death and destruction across the Great Lakes region. One of the common problems back then was a lack of a common police frequency between the various Midwestern States to relay information back and forth. Prior to that time, starting at the turn of the 1950s, each area of Michigan had its own frequencies that were very popular for interoperability, albeit very limited back then:
37.100 Civil Defense Intercounty, often used by police as well in the L.P.
39.140 Intercounty in the Lower Peninsula.
39.580 Intercounty Mutual Aid/Civil Defense in the Upper Peninsula.
39.820 Intercounty Mutual Aid/Civil Defense in the Lower Peninsula.
In addition, many fire departments often used 39.580 and 39.820 as their main fire freqs well into the early part of the 21st Century. Further, the MSP sought to consolidate the two aforementioned VHF-Low band frequencies into a VHF-High band channel called the Michigan Emergency Public Safety System (MEPSS) in 1965. This was mostly due to the large amount of skip radio traffic being received on the lower frequencies back then.
Before the creation of the MPSCS, 155.370 is officially known as "Point-to-Point," across the state, which exception of the Detroit Metro area, which for the most part, call it "Intercity." Likewise, since all of the neighboring states use it for the same purpose, you will often hear Michigan departments talking with neighboring agencies along the state line, especially when there is a high-speed pursuit, or severe storms approaching. Moreover, since each of the neighboring states are implementing full-coverage, statewide trunked radio systems, activity in those areas is also decreasing on 155.370. However, it will be used for the next few years at least, or can be a viable, redundant backup to any TRS currently in place.
