4265-9
Geometric Design Guide
for Bridges on Local Roads and Streets, Not Having State Route Numbers
Geometric design standards shall be
in accordance with the AASHTO publication "A Policy on Geometric Design of
Highways & Streets", Local Roads and Streets, 2004, p. 386.
I.
Minimum
Bridge Widths
A.
Rural
section (2 lanes without curb)*
|
Speed Design |
Design Year |
Bridge Width |
Design ** |
|
All Speeds |
0-399 |
TW + 2 ft + 2 ft (TW + 0.6 m + 0.6 m) |
HS-20 (MS-18) |
|
All Speeds |
400-2000 |
TW + 3 ft + 3 ft (TW + 0.9 m + 0.9 m) |
HS-20 (MS-18) |
|
All Speeds |
Above 2000 |
TW + 8 ft + 8 ft (TW + 2.4 m + 2.4 m) |
HS-20 (MS-18) |
TW = Traveled Way (Lane Widths)
*For low
volume roads with an approach roadway width of one lane, a minimum bridge width of 18 ft may be selected with the
concurrence of the Chief Engineer.
** For
bridges designed utilizing the LRFD Bridge Design Specifications, the design
live loading shall be HL-93.
B. Multilane rural (undivided-- 4 or more
lanes)
|
TW + 16 ft (4.8 m) |
8 ft (2.4 m) shoulders right and
left |
C. Multilane rural (divided)
|
TW + 12 ft (3.6 m) |
4 ft (1.2 m) inside shoulders + |
D.
Urban section (with curb)
The
minimum clear width for all new or reconstructed bridges shall be the curb to
curb width of the approaches except that the minimum curb to curb width for
two-lane, two-way bridges shall be TW + 4 ft (1.2 m) unless an exception is
obtained from the Chief Engineer. Sidewalks shall be provided on bridges where
curb and gutter is provided on the approach roadway. Minimum sidewalk width on bridges
shall be 5.5 ft (1.7 m).
II.
Vertical
Clearance
Vertical
clearance shall be a minimum of 16.5 ft (5.1 m) on all rural highway
separations with 17.5 ft (5.4 m) minimum where the bridge design is such that
future jacking is not practical. A minimum vertical clearance of 14.5 ft (4.4 m)
is permissible in rural or urban areas on low volume roads (under 400 ADT)
where a suitable bypass for high vehicles is available.
III.
Bridge
Widenings
When an
existing bridge is to be widened, its structural capacity will be accepted if
the live load capacity is HS15-44 (MS 13.5) or greater. For bridges that are to
be widened on the State Grip System, the structural capacity will be accepted
if the live load capacity is HS-20 (MS-18) or greater.
IV.
Design
Variances
When a
project is implemented using Federal Funds and the structural capacity and/or
width characteristics do not meet the above criteria, a design request variance
will be submitted to the Chief Engineer for approval.
Document History:
- submitted by Division of Preconstruction
- issued: 09/02/86
- revised: 10/08/96
- added to TOPPS: 01/02/97
- title changed: 03/30/01
- title changed: 08/22/02
- revised: 12/30/03
- reviewed: 01/27/05
- reviewed: 03/08/08
- revised: 07/14/08
