It is apparent from this table that the ratio of engine size to
the fuel flow rate does not remain constant over the range of vehicles
considered. In effect, using those ratios to calculate the rate for a
vehicle size of 1500 c.c. would result in a range of value from 0.94
to 1.5 l/h. It is interesting to note that this spread of values is
not incompatible with that found for a single vehicle in tests undertaken
by Robertson et a1 [19801 when the idling rate ranged from 1.0 to 1.5 l/h
depending on tuning conditions.*
After considering the rates reported for vehicles whose engine size
is similar to the average [Table 21, it was decided to use a central
value of 1.2 l/h when buildjng a fuel consumption sub-model to reflect
average urban driving conditions.
. . . ... ... ... ... ... . . . ... ... ... ... . . .
* This refers to the Glasgow test reported in Robertson et a1 (19801
and was confirmed by Or. 0.1. Robertson in private communication.