The high-level tunnel reaches existing streets at Washington Avenue. From this point is planned a system of thoroughfares, which, if constructed, would reach all parts of the South Hills. These thoroughfares are indicated by dashes beyond the junction of the tunnel with Washington Avenue.
The Bell House, or low-level tunnel is indicated by a dotted line. It is an approach to the West Liberty Road and would give easy access only to the territory reached by that road and to other territory in the nearby valley bottoms.
The above diagrams show the areas that can be reached via the low-level and high-level tunnel routes to the South Hills, on a maximum gradient of 3½ per cent, by hauls of various lengths from City Hall. The areas are given in the following table:
| Length of haul from City Hall | Total area reached | Amount of land sloping over 25 per cent | Remaining land available for use | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Low-level route | High-level route | Low-level route | High-level route | Low-level route | High-level route | |||||||
| 2½ miles | 156 | acres | 1091 | acres | 86 | acres | 373 | acres | 70 | acres | 718 | acres |
| 3 miles | 672 | " | 2710 | " | 293 | " | 848 | " | 379 | " | 1862 | " |
| 3½ miles | 2763 | " | 4877 | " | 1053 | " | 1617 | " | 1710 | " | 3260 | " |
| 4 miles | 6329 | " | 7408 | " | 1935 | " | 2449 | " | 4394 | " | 4959 | " |
But even without precise data, it is clear that the best permanent means of reaching those upland districts, whether on one side of Sawmill Run or on the other, is not by a tunnel debouching in the bottom of the valley—say at the Bell Tavern. This follows from the fact that the tunnel can reach a much higher level at a good gradient and with a shorter distance. And from this higher outlet point a viaduct high in the air above the Bell Tavern would give direct access to the uplands of Beechview and Mt. Lebanon and southward, while streets of easy gradient would reach the uplands east of Sawmill Run. The high level tunnel, furthermore, will reach all the areas served by the low level, or Bell Tavern, route, and in addition can reach the other and more important lands on the hills which cannot be reached via the Bell Tavern route within a reasonable distance.
The thoroughfare extensions from the southern end of the tunnel are briefly discussed under "Outlying Thoroughfare Improvements" below. At its northern end the new bridge would fit admirably into the proposed thoroughfare system of the Down Town District, main wide streets extending directly from the end of the bridge approach to the north, south, east, and west.