occupying the street-car space, would prevent the other automobiles from passing quickly the slow vehicles. This cutting of the speed in two does not by any means halve the capacity of the bridge, but it certainly reduces it materially, possibly to 75 per cent; because the space between vehicles would reduce with the decrease in velocity. The greater the number of

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horse-drawn vehicles on the bridge the slower would be the average speed of the procession in the other line; and with a great many of them on the roadway, the automobiles would naturally confine their travel mainly to the street car line and adjust their speed to that of the cars.

It is evident, therefore, that, before designing any transbordeur, one should study carefully both the present and the probable-future proportions of all  kinds of travel and adjust the design upon the principle of  "the