Page 45 - Bridge and Highway Structure Rehabilitation and Repair

20 SECTION 1 ADMINISTRATIVE ISSUES

Table 1.4 Minimum vertical clearances.
Minimum
Serial Number Located over Vertical Clearance Remarks
1 Interstate highway 161–62 (5.03 m) Freight trucks with unusual height to
utilize selected routes
2 State highway 151–62 (4.72 m) Height caters for most of trucks

3 Local street 141–62 (4.42 m) Minimum truck traffi c required on
local streets
4 Pedestrian 171–62 Comfort of walking with the least noise
from traffi c above
5 Waterway Usually determined Applicable only for navigable rivers
by Coast Guard

6 Over railroad 231–02 Trains with special freight height

height trucks than those on highways today. Any deviation needs to be posted as warning
signs to prevent accidents.
3. Vertical clearance requirements: Minimum requirements are based on the importance of the
highway. It would be uneconomical to design all bridges to a single horizontal or vertical
clearance requirement rather than based on their importance and frequency of use. Some
bridges may have additional levels for carrying traffic, e.g., George Washington Bridge,

New Jersey.
In such cases there would be top level, bridge deck level, and lowest level such as highway,
railroad, or navigable river in a direction at a right angle.
4. Each highway agency can modify clearances to a certain acceptable extent from those laid
down by AASHTO. These variations need to be approved by AASHTO before the state

Figure 1.9 Vertical under clearance requirement for a railroad.