single travel mode construct for arcgis rest appi using json call

[James_001]

I am trying to figure out how to construct JSON requests to get a single travel mode for my rest service. My rest service is already configured with 4 travel modes, I can retrieve travel modes from the retrieveTravelModes call. But if I want to use anyone what request of JSON I should use? I am using this help from ESRI online help. I am not sure how to provide travelMode parameters inside of my JSON request.

https://developers.arcgis.com/rest/network/api-reference/closest-facility-synchronous-service.htm

https://developers.arcgis.com/rest/network/api-reference/closest-facility-synchronous-service.htm#ES...