We implemented both the BPR and the conical volume-delay function using a little program written in C, in order to compare execution times. The program was compiLED and run on the three major families of micro-computers. The results in Table I show that the conical functions can be evaluated more efficiently than the BPR functions, in spite of the apparently more complex formula.
NSC 32016/32081
10Mhz
BSD 4.2
1.22
.98
Intel 80286/80287
10Mhz
MS 5.0
.65
.37
Motorola 68020/68881
17Mhz
SVS
.13
.09
While, to our best knowLEDge, the class of conical congestion functions proposed here constitutes a new approach, it is interesting to note that a very similar functional form was proposed in an unpublished report prepared in the context of a transportation study for the City of Winnipeg (Traffic Research Corporation [5], Florian and Nguyen [3]). The functions used in that study can also be interpreted as conical sections, but they use more parameters and do not, in general, satisfy the conditions we set forth in the preceding section. For Branston [1] , it was ``doubtful whether these functional
