Ministry of Transport and Public Works

Evaluation of the Delft Bicycle Network Plan

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EFFECTS OF THE DELFT DICYCLE NETWORK PLAN - Effects on mode choice constraints

Choice of mode decision by a traveller for a specific trip has been analysed in the evaluation study in terms of so called choice constraints, which prevent travellers from choosing certain modes. These choice constraints may be very different and vary from objective restrictions, e.g. no bicycle is available, to very subjective reasons, e.g. traveller hates cycling. The bicycle traffic infrastructure may also cause choice constraints.

It is important to know to what extent the bicycle network plan succeeded in removing constraints that prevent travellers from choosing the bike and thereby enlarging the class of travellers having a choice (unconstrained travellers). The class of trips for which the bicycle might be chosen is called 'cycling potential'. Three questions were dealt with in this respect:

1. Did the constraints with respect to bicycle use diminish between 1982 and 1985 ?
2. How did the bicycle network plan remove constraints?
3. Did competition between bicycle and the other modes change?

1. Decrease in constraints

   Figure 8 (a,b) shows the proportions of unconstrained non-bicycle trips in 1982 and 1982 for both the study and the control area. The shares of non-bicycle trips having objective and subjective choice constraints respectively are indicated too. From the figure it can be seen that in both areas constraints against cycling clearly diminished. The group of unconstrained trips with respect to bicycle use, i.e. the bike could have been used for these trips, almost doubled its size to ca. 32 per cent.
   A striking result is that this large increase is mainly caused by a reduction in the objective restrictions. This type includes two specific constraints. The first one is "no objective possibility of choosing the bike", referring to reasons like 'do not own a bike' or 'can not cycle'. The second constraint is called 'compelling reasons', including luggage, health reasons, car needed during work, etc.. The occurrence of the second type of constraint fell most from 30 per cent to 22 per cent.
   This finding applies equally to both car and walking trips, although these modes serve rather distinct travel market segments.

2. Effect of bicycle network plan on choice constraints

   The contribution of the bicycle network plan on the increase of the unconstrained travellers with respect to bicycle use has been established by:
   
   

   1. comparing the study area and control area results,
   2. analysing in detail the occurrence of specific constraints.

   Figure 8 (a,b) indicates that the proportion of choice travellers among non- bicycle trips ('cycling potential') is almost identical in the study and control area. This similarity was found both for 1982 as for 1985, implying equal changes in both areas.

   Figure 8: Changes in choice constraints in study and control area between l982 and 1985

   As was mentioned earlier the removal of objective constraints was the main cause of the growth of the share of choice travellers. No measures taken as part of the bicycle network plan can have contributed to these changes, since the objective constraints deal with bicycle ownership, health, long trip distances, luggage etc..

   For both areas and both points of time, table 9 gives the possibility of choosing the bicycle for non-bicycle trips, as well as the limiting effect of six types of constraints. The table starts with 100 per cent unconstrained trips and successively subtracts the percentage of trips that is bound to the used mode because of a particular constraint. In the case of trips of study area inhabitants in 1982 (first column), 12.4 per cent of the non-bike trips do not have an objective possibility of using the bicycle. Of the remaining S7.6 per cent of these trips, 31.5 per cent have compelling reasons against bike use. Thus, only S6.1 per cent remains unconstrained at that stage; and so forth.

   The striking resemblance of the contributions of each constraint between study and control area is maintained after the implementation of the plan. This leads to the conclusion that the comparison of both areas with respect to frequencies and changes in the occurrence of constraints does not provide evidence of a significant effect of the bicycle network plan.

   Table 9: Choice restraints of non-bicycle trips, all modes

3. Changed competition between the bicycle and other modes

   This conclusion is also supported by the occurrence of the subjective constraints which would have been affected by the plan. The 'perceived road and traffic conditions' appears to be an insignificant restriction. 'Perceived travel time' is an important subjective constraint but its occurrence remains unchanged.
   The final conclusion of this analysis is therefore that the group of travellers that may choose the bicycle has increased, but that the bicycle network measures did not have any influence.

   The previous section showed that the proportion of non-bicycle trips that may choose the bike nearly doubled. This large increase in bicycle potential stems from the car and walking modes, because of their large modal shares.
   Conversely, an important question is whether bicycle trips may choose other modes to a larger extent. It is assumed that the bicycle network plan does not affect this choice possibility. Therefore, ITS has investigated this aspect for all areas combined.

   Figure 8 (C) shows that the share of unconstrained bicycle trips also increased between 1982 and 1985. This class of cyclists, who may choose other modes, increased from 41 to 56 per cent. It is remarkable that this growth is caused by an increased possibility of cyclists to choose walking. This may be explained by the fact that a number of travellers that walked in 1962, cycled in 1985. These cyclists may easily switch back to the walk mode.

   The general finding is that all categories of travellers have got more choice options. This enlargement of the choice set means an advantage and at the same time a disadvantage to the bicycle mode. Competition has become tougher. It offers the possibility of attracting more travellers to the bicycle mode by improving this mode substantially.