THEORIES FOR TOLL TRAFFIC ENGINEERING IN THE U. S. A. 



489 



pertinent load-loss relationships. The methods so far discussed, and 

 proposed for use, will be briefly reviewed. 



The dimensioning of each high usage group of trunks is expected to be 

 performed in the manner currently in use, as described in Section 7.6. 

 The critical figure in this method is the load carried on the last high 

 usage trunk, and is chosen so as to yield an economic division of the 

 offered load between high usage and alternate route trunks. Fig. 40 is 

 one form of load-on-each-trunk presentation suitable for choosing eco- 

 nomic high usage group size once the permitted load on the last trunk 

 is established. 



The character (average a and variance v) of the traffic overflowing 

 each high usage group is easily found from Figs. 12 and 13 (or equivalent 



- OST GROUP NO. 2 



4 5 6 



TRUNK NUMBER 



CROSSBAR TANDEM GROUP 



Z 

 O 



2 4 



6 8 10 12 14 16 18 20 22 



TRUNK NUMBER 



SUBURBAN TANDEM GROUP 



12 4 6 8 10 12 14 16 



TRUNK NUMBER 



Fig. 41 — Comparison of load carried by each alternate route trunk; theory 

 versus throwdowns. 



