(MOPTMA, 1993) and the parking cost, for the bus we use a pondered average bond-bus
and the usual ticket and then we calculated the difference.
Time of travel. This variable is calculated like the difference of total time spent in the travel
by car and by bus expressed in minutes, we needed esteem the time of the non-chosen
alternative for each individual to be able to calculate the differences, because like we have
commented, the way of transport is chosen depending on the difference in time between
urban and private transport.
2.- SOCIOECONOMIC VARIABLES
Relation with the head of the family. This variable can be interpreted like a proxy of the
availability of vehicle, although it is not determinant of the chosen way of transport. It will
take value 1 for the head of the family and 0 for the rest of the cases.
Sex. Like the previous one it is a proxy of the possibility to have a vehicle that takes 0
value for women and 1 for men.
Age. It will give us information if there are rules of different behaviours for the choice of
the way of transport, depending on the individual´s age. This variable was divided in two
groups choosing like a reference the group of younger than 35.
Professional situation. This is a proxy variable of the rent level, because we do not have this
variable, was divided in three groups; bosses and superior workers (Profession 1) the other
workers with a boss (Profession 2) and own workers (Profession 3), taken the this like
reference.
Defined the variables we esteemed the function of private transport demand along the
probit model, getting the results in charts 1, 2 and 3.
In the trhee models, all the variables as the offer ones as the socioeconomic ones appear
with the expected sign although not every ones are important. The variables that gather the
transport caracteristics are in every case important to 5% but, the influence of a variation in
the difference in time over the probability to choose private transport, is always over the
same variation of the difference in prices. These results make us think that a reconstruction
of the buses net, that would suppose a bigger adequacy between offer and demand and an
increasing of the frequency and the speed, joined to an appropiate rate, will increase the
probability to choose urban transport.