This is only used in California. Only one other Forest Service Region I know of that has a travel net is the Intermountain Region (southern Idaho, Utah, southwest Wyoming, and Nevada) and it only extends into Utah and southern Idaho. Nothing in Nevada and Wyoming as far as I know. There are 20 repeaters on the system which utilizes 168.175 output and 164.825 input with telephone autopatch and sub-audible access.
Travel nets were conceived and built in the late 70's and 80's with the redirection of fire resources being a large concern along with communication for non-fire personnel when traveling for meetings, training, and details on other Forests. The last 10-15 years has seen a shift away from the use of radio and more use of cell phones. Other regions have also designated "travel nets" that don't include repeaters or any way to call base stations. In Region 3 (Southwest Region - Arizona and New Mexico) they use 168.350 as a travel net. Using a frequency other than the NIFC tacticals is the goal when units traveling together are on the road. Engine (five engines and the strike team leader's vehicle) and dozer strike teams (two lowboys and the strike team leader's vehicle) and the three vehicles used to transport crews (2 ten person crew buggies and the superintendent's pickup) need to talk with each other and for years they would use Tac 2 (168.200) or their home unit's frequency on direct. This caused interference with other Forests and with other fires so they try to discourage it in favor of the travel nets.
I used to monitor travel net all the time when I went on fires and still do in retirement when I take a road trip. I refused to have a cell phone at work because I did not want to have desk jockeys calling me all the time when I was in the field. I was taking a crew from a fire on the Los Padres to one south of Idllywild on the San Bernardino and unknown to me had been given an order to divert to a fire on the Angeles. We drove all the way south of Idllywild, arriving at 2 a.m. to a fire that had been contained early in the evening, and found everyone in camp sleeping. We bedded down for a few hours and got up with the camp about 5 a.m. to find we were supposed to be on a fire north of Castiac Lake on the Angeles. We had to drive across the L.A. Basin once again. South Ops never tried nor was it indicated that we should monitor travel net to listen for South Ops giving diversion orders. They only did so via cell phone, so we had to cross the L.A. Basin in evening traffic and then cross it the following day during the morning commute. Not what I would call efficient. Since none of the crew's handhelds had the travel net programmed in we used good old Tac 2 or Crew Net as it was called for about 3 decades to communicate what lane to be in to make the transition from one freeway to the next.
Ironically, being the travel net was conceived by the Forest Service, the only units I ever hear using travel net is CDF and that just being between each other. The repeaters are nice in case someone gets out of direct range. I've never heard South or North Ops or any Forest dispatcher on the net, even though the original plan for the network showed all the repeaters linked into each center depending on its location.
By the way, the year I took the crew out and did not have a cell phone was 1996. By the time I retired I had been told I had to obtain two different items, a cell phone and a pager with a message screen. I dragged my feet and ended up retiring before the ax fell as far as the due date for me to get them. I ended up retiring a few years early on a medical disability on very short notice. I had a voice pager that worked on Forest Net and when dispatch wanted me they paged me. The non-fire people wanted easier access to me and wanted me to have a newer pager and the cell phone. I felt that when in the field I should concentrate on field tasks and not answering phone calls from admin type people who really didn't need me until I returned to quarters and returned their calls. The other times I took out crews I just took over someone's USFS cell phone and listed that number with dispatch as the point of contact, so I never had to take unnecessary trips again.