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of 28 feet when the river is at a 15-foot flood stage. This height to be maintained over the entire main span where there is a central span and for 180 feet on each side of the central pier where there is a central pier.

We have the honor to be, very respectfully,

Your obedient servants,

THOMAS W. SYMONS
Col. Corps Engineers U. S. A., retired,

FREDERICK LAW OLMSTED.

APPENDIX I

Amount and Importance of Bridge Traffic. - Highway Bridges. -- The following table gives the records of counts made in the fall of 1909, and spring of 1910 on the various bridges over the Allegheny River:

RECORD OF COUNTS. -- TABLE No. 1

Location of bridges	Period of count	Street cars	Heavy wagons	Light wagons	Carriages	Automobiles	Pedestrians
Sixth Street	Aug. 24 - Oct. 23	89,354	55,791	79,247	9,534	24,583	1,605,793
Ninth Street	Aug. 26 - Sept. 30	72,854	8,961	14,846	613	960	185,158
Sixteenth Street	Oct. 4 - Oct. 17	. . .	*4,444	*7,764	. . .	. . .	76,495
Thirtieth Street	Aug. 24 - Oct. 23	. . .	9,844	10,184	667	447	96,485
Forty-third Street	Aug. 23 - Nov 1	. . .	8,159	8,165	987	2,179	130,744

RECORD OF COUNTS. -- TABLE No. 1A**

Location of bridges	Period of count	Passenger vehicles	Delivery vehicles	Single trucks	Double trucks	Pedestrians
Seventh Street	Feb. 28 - Mar. 3, 4, 5, 7	401	4,800	273	1,035	29,146

*Automobiles and carriages included in counts for light and heavy wagons.

**Table 1A. The count at Seventh Street bridge was recorded by different units and, therefore, required a separate table. The North Side approach to this bridge was being improved at the time the count was made, causing a temporary interference with travel reflected in an abnormally small proportion of traffic on the bridge and a corresponding increase for the adjacent bridges.

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Last modified on 22-Dec 1999
Design format: copyright 1997-1999 Bruce S. Cridlebaugh
Original document: Frederick Law Olmsted, 1910