Highway Engineering

(Note, if Equation 2.2 is used within the trip distribution process, the rows

sum correctly whereas the columns do not. In this situation the row-column

factor method is again used but the two-stage process is reversed as a correc-

tion is first applied to the column totals and then to the new row totals.)

2.8.3 Modal split

Two modes of travel are available to all trip makers within the interchange

matrix: bus and private car. In order to determine the proportion of trips under-

taken by car, the utility of each mode must be estimated. The utility functions

for the two modes are:

(2.19)

(2.20)

where

C=cost (£)

T=travel time (minutes)

For all travellers between each pair of zones:


 The trip by car costs £2.00 more than by bus


 The journey takes 10 minutes longer by bus than by car.

Since the model parameters for the cost and time variables are the same in

Equations 2.19 and 2.20, the relative utilities of the two modes can be easily

calculated:

Ucctt()BUS CAR- =-()--+()()-+()()-

=- + -

=-

00 25 06 2 001 10

25 12 01

14

....

...

.

UCTBUS=- -00 06 001...

UCTCAR=- -25 06 001...

40 Highway Engineering

Destination zone

Origin zone A B C D E F G Total

A1 2286 2112 3 352 1 551 1 780 918 22 000

B 1670 0 1800 5 599 1 152 918 361 11 500

C 1407 8 818 0 4 144 1 114 1 528 489 17 500

D 632 7 759 1172 0 2 722 1 757 458 14 500

E 1222 6 673 1317 11 380 0 2 360 3 548 26 500

F 998 3 784 1286 5 226 1 680 0 4 526 17 500

G 547 1 579 437 1 448 2 681 4 807 0 11 500

Total 6475 40 900 8125 31 150 10 900 13 150 10 300 121 000

Table 2.22Final corrected trip matrix