Total posts : 45366
I just read the report, and there are some holes. If two vehicles happen to be in the detection zone at the same time, and transmitting on the same channel, then isn’t the field strength going to be much higher? Also using a average distance between the lanes of traffic is really very flawed. If a part 15 FM has a range of about 200 feet, then the signal strength over a distance of twenty or forty feet is going to be an large variance (difference between the closest and farthest lanes). Two lane roads are approximately 20 feet wide or more, 4 lanes roads are going to be more like 40. I’ll give them something for the effort, but unless you can sample a single lane then things are not going to be accurate enough. They would be better off trying this in a tunnel where you can put the antenna in the average width of the road. Maybe on a bridge would work too. The only other way to do this is to move the receiving antenna far enough away from the traffic that the distance between the cars is very small compared to the distance between the cars and the antenna.
Footnote, normal highway lane widths are slightly more than 12 feet wide between the painted lines, plus the shoulder area. Vehicles can not be more than 12 feet wide without a special permit. If my memory is correct, more than 10 feet wide requires a “wide load” sign, but I could be wrong.
