The high cost of urban transportation has invariably fallen most heavilyon the poorest classes, who pay a higher proportion of family income to 62.______transportation, and often cannot find adequate means of reachingemployment. In modern industrial centers new jobs tend to locate away from 63.______file congested districts where the poor traditionally live.Normally walking speed for a man has remained at about 3.1 miles perhour at the beginning of recorded history. Horses and horse-drawn omnibuses 64.______raised the speed of travel to approximately 6 miles per hour. Buses andtrolleys providing average speeds of 5 to 6 miles per hour in rush-hour traffic 65.______to 12-14 miles per hour on most city streets in other time periods. Speed ofup to 50 miles per hour are often reached by buses in outlying streets of largecities, but schedule speeds, which include stopping times, are much higher. 66.______Studies of relative speeds of principle mid 20th-century urban-transitmodes showed average automobile speeds of up to 10 miles per hour,compare with 16 miles per hour for suburban rail roads, and substantially less 67.______for other mass transit. When doubtless valid statistically, such studies are 68.______misleading because of the different functions of the different types of transitTo gain a real picture of urban transit speeds in a city like Paris or New Yorkwould require a rationale that included a number of persons moved per mile, 69.______how near the center of the city the movement took place, and aim stationspacing. Broadly speaking, what may be said that while speed of movement, 70.______especially during rush hours, still leaves something to be desired in mostcities, it is as critical a problem as that of costs. 71.______ 64（）