Difference between revisions of "231.8 Bridge Width"

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(Per BR, Criteria for minimum bridge width expanded to include National Bridge Inventory rating system requirements for bridge width)
(Per BR, revision coordinated with Green Book guidance that clear bridge width shall be the same as the approach roadway for collectors, arterials and freeways.)
 
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Bridge width will vary based on project scope, context of surrounding road, future plans for the route, and Deck Geometry rating (NBI Item 68). Project scope and bridge economics usually determine the treatment strategy for individual projects. Treatment strategies range from new, replacement, widening, redecking and rehabilitation bridge construction.
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Bridge width, exclusive of sidewalks, shall be equivalent to the existing or, if wider, proposed approach roadway (i.e., traveled way and any shoulders) width. In the absence of shoulders, the bridge width shall be 4 ft. (2 ft. per side) wider than the approach traveled way width. Greater bridge widths may be considered if future expansion of the facility will occur within the first half of the expected life of the bridge improvement, shared-use lanes will be constructed immediately adjacent to the roadway, or to facilitate construction.  
 
 
'''Major Roads'''
 
 
 
The desirable width of bridges on Major roads is equivalent to the width of the traveled way and any existing or proposed shoulders. The minimum width of bridges for Major roads is 24 ft., that is, there could be situations where an existing bridge may be rehabilitated and used in place even though it may not be the desirable width.
 
 
 
'''Minor Roads'''
 
 
 
The desirable minimum width of bridges on Minor roads is equivalent to the width of the traveled way and, 1) any existing or proposed shoulders or, 2) 2 ft. shoulders, whichever is greatest.
 
 
 
'''Major and Minor Roads (Based on NBI Deck Geometry Rating)'''
 
 
 
The bridge width based on Major/Minor Roads classification could conflict with the minimum bridge roadway width based on the Deck Geometry rating of  the National Bridge Inventory (NBI) rating system. FHWA requires all bridges on public roads to be inventoried and inspected in accordance with the National Bridge Inspection Standards (NBIS) within which the NBI operates. The FHWA holds MoDOT responsible for collecting and submitting the bridge inventory data for all bridges within the state.
 
 
 
The engineer should determine the roadway width of the bridge based on site-specific conditions. Once this width is determined, it should be checked against the following table in order to evaluate if new, replacement, widening, redecking or rehabilitation bridge construction would be considered to be deficient based on its deck geometry. If the proposed bridge roadway width is less than that shown in the following tables, the width provided in the table should be used or a design exception could be considered. Only under extraordinary circumstances should a design exception be considered for new or replacement bridge construction since the goal at MoDOT and FHWA is to reduce the number of deficient bridges and also since funding sources for bridge construction could be influenced. For other types of bridge construction, design exceptions should be considered under normal circumstances.
 
<center>
 
===Minimum Bridge Width Based on Deck Geometry Rating<sup>1</sup>===
 
 
 
 
 
{| border="1" class="wikitable" style="margin: 1em auto 1em auto" style="text-align:center" width="800"
 
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! style="background:#BEBEBE" |Roadway Classification||style="background:#BEBEBE"| Facility Type<sup>2</sup>||style="background:#BEBEBE"| Future or Design ADT<sup>3</sup>||style="background:#BEBEBE"|Width<sup>4</sup> (Ft.)
 
|-
 
|rowspan="11" |Major||rowspan="6" |2-Lane/2-Way|| < 100 ||18
 
|-
 
|101 - 400||20
 
|-
 
|401 - 1000||22
 
|-
 
|1001 - 2000||24
 
|-
 
|2001 - 5000||28
 
|-
 
|>5000||32(28)<sup>5</sup>
 
|-
 
|2-Lane/1-Way||rowspan="5"|All||34(29)<sup>5</sup>
 
|-
 
|3-Lane/1-Way|| 45(40)<sup>5</sup>
 
|-
 
|4-Lane/1-Way|| 56(51)<sup>5</sup>
 
|-
 
|5-Lane/1-Way|| 67(62)<sup>5</sup>
 
|-
 
|6-Lane/1-Way|| 78(73)<sup>5</sup>
 
|-
 
|rowspan="11" |Minor||rowspan="6"|2-Lane/2-Way||< 100|||18
 
|-
 
|101 - 400||20
 
|-
 
|401 - 1000||22
 
|-
 
|1001 - 2000||24
 
|-
 
|2001 - 5000||28
 
|-
 
|>5000||32(28)<sup>5</sup>
 
|-
 
|2-Lane/1-Way||rowspan="5"|All||30
 
|-
 
|3-Lane/1- or 2-Way|| 39
 
|-
 
|4-Lane/1- or 2-Way|| 50
 
|-
 
|5-Lane/1- or 2-Way|| 61
 
|-
 
|6-Lane/1- or 2-Way|| 72
 
|-
 
|rowspan="3"|Ramp||1-Lane/1-Way||rowspan="3"|All||18
 
|-
 
|2-Lane/1-Way|| 28
 
|-
 
|3-Lane/1-Way|| 40
 
|-
 
|colspan="4" align="left"|'''<sup>1</sup>''' Table based on NBI Item No. 68 - Deck Geometry of the ''Recording and Coding Guide for the Structure Inventory and Appraisal of the Nation's Bridges''.
 
|-
 
|colspan="4" align="left"|'''<sup>2</sup>''' Where facility type is not listed, see State Bridge Engineer.
 
|-
 
|colspan="4" align="left"|'''<sup>3</sup>''' Includes ADT for both directions of traffic, where applicable.
 
|-
 
|colspan="4" align="left"|'''<sup>4</sup>''' Minimum width is based on a deck geometry code = 4, which is defined as "meets minimum tolerable limits to be left in place as is".  Any width less than this will result in a deficient bridge width (i.e., bridge would be considered functionally obsolete).
 
|-
 
|colspan="4" align="left"|'''<sup>5</sup>'''  May use value in parenthesis for bridges longer than 200 ft.
 
|}
 
 
 
 
 
  
  
 
[[category:231 Typical Section Elements for Roadways|231.08]]
 
[[category:231 Typical Section Elements for Roadways|231.08]]

Latest revision as of 12:18, 13 August 2018

Bridge width, exclusive of sidewalks, shall be equivalent to the existing or, if wider, proposed approach roadway (i.e., traveled way and any shoulders) width. In the absence of shoulders, the bridge width shall be 4 ft. (2 ft. per side) wider than the approach traveled way width. Greater bridge widths may be considered if future expansion of the facility will occur within the first half of the expected life of the bridge improvement, shared-use lanes will be constructed immediately adjacent to the roadway, or to facilitate construction.