From the Trainz Wiki page at
https://online.ts2009.com/mediaWiki/index.php/KIND_Track
isroad
If set (1), splines of this type are considered roads. Roads support the generation of Carz. Roads are flagged as blocked by
KIND MOCrossing while the crossing gate is closed. Road splines can generally be joined, even if they are different assets.
If not otherwise specified, assets with the 'isroad' tag set are members of the "Road Spline Group"
<kuid:30501:100045>.
[
My Edit: Presumably, if isroad is set to 0 then that will negate all the following traffic controls and stop the traffic. If so I would love to use this on the roads around where I live]
carrate
(Only applicable to splines which have 'isroad' set.)
The game waits between 1 and 3 times this value (in seconds) between generating traffic on this road.
traffic-speed
(Only applicable to splines which have 'isroad' set.)
Defines the carz speed limit of the road in meters per second. Carz currently travel at up to 80%-110% (depending on the car) of the speed limit, except when overtaking. This tag does not relate to trains in any way.
isfreeway
(Only applicable to splines which have 'isroad' set.)
If set (1), this boolean tag causes a multilane road to act as a freeway. This allows carz to change lanes at will, and causes all traffic to flow in the spline's forward direction only. Overtaking is still allowed on non-freeway roads.
numlanes
(Only applicable to splines which have 'isroad' set.)
Defines the number of carz lanes on a road. Each lane is considered to be 1.7 meters wide. If the road is a freeway, all traffic flows in the same direction. TBD: What, if anything, does this mean for a non-freeway road?
If not otherwise specified, assets with the 'istrack' tag set are members of the "Track Spline Group"
<kuid:30501:100043>.
Try it and see.