Click for next page ( 27

The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement

Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 26
26 curbs. States were asked to separately rank the functional purposes of vertical and sloped curbs used in their state. Most states identified drainage control as a primary or secondary purpose for vertical curb. Walkway support and pavement delineation were also highly rated as typical functional pur- poses of vertical curb. Only one state said the primary use of vertical curb was to protect vehicles from steep slopes. Respondents also identified other functional purposes of ver- tical curb not listed on the survey, including minimizing Figure 17. AASHTO vertical curb Type A (1 = 25.4 mm). right-of-way impacts, access control, accommodating pedes- trians, aesthetics, erosion control, delineating edge parking, and traffic channelization. The primary functional purpose of sloped curb was most used 76-mm asphalt or 100-mm lip curbs for design speeds often listed as drainage. Twenty-four states listed it as the pri- greater than or equal to 80 km/h. State 19 responded that it mary or secondary purpose. Pavement delineation was listed did not restrict their use, but noted that the policy was that by 14 states as a primary or secondary functional purpose. curbs are undesirable for use on roadways with design speeds One state listed walkway support as a primary functional greater than 80 km/h. State 24 also responded that it did not purpose, and several others listed it as a secondary purpose. restrict their use, but its roadside design guide prohibits the Protecting vehicles from slopes was listed as a secondary pur- use of nonsloped curb on new construction projects on high- pose by three states. Respondents also wrote in other func- ways with operating speeds greater than or equal to 80 km/h tional purposes of sloped curb including erosion control, and along the mainline of Interstates, freeways, or high-speed minimizing right-of-way impacts, access control, pedestrian parkways. needs, channelization, and delineation. TYPICAL FUNCTION OF CURBS ALTERNATIVES TO USING CURBS AASHTO lists drainage control, pavement edge delin- Eight survey respondents had found an alternative to using eation, right-of-way reduction, aesthetics, delineation of pedes- curbs for one or more of the functional purposes mentioned in trian walkways, reduction of maintenance operations and the previous section. State 5 used sloping freeway curbs with assistance in orderly roadside development as purposes of catch basins to prevent embankment erosion in the gutter on Figure 18. AASHTO sloped curbs (1 = 25.4 mm).

OCR for page 26
27 TABLE 5 Vertical and sloped curb use among the states surveyed Number of states Number of states AASHTO curb using a curb similar Total using this curb to this curb Type A Vertical 5 3 8 Type B Sloped 6 7 13 Type C Sloped 5 2 7 Type D Sloped 6 1 7 Type E Sloped 3 1 4 Type F Sloped 0 1 1 Type G Sloped 2 3 5 A1 A2 A3 A4 A5 A6 A7 Figure 19. Curbs used by various states that could not be classified as AASHTO curbs.