twenty-foot pavement might be about five miles an hour greater than on the twelve-foot pavement, this makes some difference-although at almost any reasonable allowance for the velue of time in developing countries, the difference would be small. the case study also neglects the impact of a wider pavement on accident reduction, which might be significant in some situations (see 'accident reduction' in chapter 4).
finally, the calculation makes no allowance for the greater comfort and convenince of on a wider pavement, especially at higher traffic levels. depending on condition of the shoulders, traveling on a twelve-foot pavement can be a nerve-racking experience.