Loading...
5 - Matters from the Board, Review and Feedback on the Broadway Reconstruction Project CEAP Appendix (4)rl ~. BROADWAY RECONSTRUCTION PROJECT APPENDIX H ~ ~ NOISE ANALYSIS ~- ~ ~ In general, u has been found that open-graded asphalt reduces no~se from 2 to 4 dB(A) when compazed to dense-graded asphalt Any no~se reducuon related to open-graded asphalt declmes w~th ume and much of ~ the benefit over dense-graded asphalt becomes non-eustent once the surface becomes more pohshed Unfortunately, open-graded asphalt can be problemauc m wet or cold chmates due to freezelthaw cycles ~ that result m roadway detenoraaon Previous stud~es were also performed to measure nase vananons generated from PCC surfaces w~th and wrthout umng. Numerous reports state that transverse umng causes the geatest no~se levels and can also lead to an untaung, pure tone no~se or "whme " Randomly spaced Umng and vaned qne w~dths have been found ro reduce both [he pure tone no~se and overall noise levels, but may sdll produce a d~screte wtune. PCC pavement with long~mdmal umng does not produce an aud~ble whme and, as noted earl~er, has lower overall noise levels than transversely uneA PCC pavement It is also generally accepted that PCC pavemenu become qmeter over Ume Table 2 presenu a summary of general compansons of pavement noise emissions measured 25 feet from the centerLne Th~s mforma~on ~s from a prev~ous study, Reference 1 The transversely uned PCC pavement is the pomt of companson for all of the other pavement types Table 2 Pavement Noise Comparison Pavement Type ~Lel Level Reduction Compared to Transversely Tined PCC Pavement Transversely Tmed PCC Pavement - Randomly Tmed PCC Pavement 1- 3 dBA L.ongitudmally Tmed PCC Pavement 4- 7 dBA Open-Graded Asphalt 5 dBA I.ongimdma] Astro-Turf PCC Pavement (no tmmg) 6 dBA T'he Broadway Reconstrucnon Pro~ect, if implemented, would employ an astro-turf drag texture PCC pavement Tmmg would not be implemented Accordmg to Table 2, PCC pavement with longrtudmal asvo-turf drag w~[hout tmmg would produce a decrease of I dec~bel when compazed to an asphalt surface, the ex~shng surface w~thm the pro~ect azea As was noted m the No~se Fundamentals sechon, a change m L.eq of less than 3 dBA ~s not percepable to the human eaz I[ ~s official pol~cy of the Federal H~ghway Adm~mstrahon (FHWA), and the op~mon of the Amencan Association of State Highway and Transportation Offictals (AASHTO), that a small reducuon in traffic noise generated from a paruculaz pavement type ~s not worth sacnficmg safety and durabiltty Conclusion Although the on-site results do no[ md~cate there ~s a derectable difference between the use of astro-turf drag concrete pavement vs asphalt m the Broadway comdor, [here aze scveral key issues to note :• Measuremenu of ex~stmg no~se levels on Broadway show no d~shngmshable dtfferences between exishng potuons of concrete pavement and asphalt pavement Based on site noise measuremenu and [he mformauon reviewed from vanous stud~es referenced a[ [he end of th~s report, the reconstrucUOn of Broadway from Umvers~ry to Pme with concrete pavement w~ll not change ex~sLng no~se levels overthe exisung condiqons /"~+ ~ ~ ~ ~ Broadway Reconstruction Project Noise Monitoring and Pavement Type Analysis September 4, 2001 Background The Broadway Reconstrucuon Pro)ec[ is bemg evaluated under the Nauonal Env~ronmental Pol~cy Act (NEPA) as a Categoncal Exclus~on (CE) The pro~ect is a federally funded pro~ect [hat does not meet the Colorado Department of Transportaaods (CDOTuFederal Highway Admimstranon (FHWA) requ~rements for a detailed noise analysis The reconstrucuon dces not matenally change the honzontal or vert~cal profile or width of the roadway and the pro~ect dces not add or change capacrty Although the pro~ect dces not requue a detailed noise analysis, asphalt pavement will be replaced wrth concrete pavement wrth an "aztro-turY' cazpet drag fimsh Th~s memorandum outhnes the methodology and conclus~ons associated w~th the replacement of the exisung pavement and any assoc~ated ~mpacts The memorandum also mcludes a compara~ve analysis of no~se euussions from several d~fferent concrete and asphalt pavement types This mformauon was obtamed from previous research and from actual measurements at the pro~ect srte ~ Noise Fundamentals Decibels (dB) are the umt by which no~se levels are measured Grven that the human eaz responds differendy to vanous frequencies, measured sound ]evels (m decibels) are generally "we~ghted" to equate to frequency response of humans and human percepnon of loudness Weighted sound levels aze expressed ~n umts called A-weighted decibels (dBA) Because transportauon-related noise generally fluctuates over ume, averagmg noise levels over a penod of hme allows a smgle number to descnbe the condmon Th~s resul[mg number captures the eqmvalent contmuous noise level or Leq A change m sound pressure levels of 3 dBA or greater ~s percept~ble to the human eaz Any change of less than 3 dBA gces generally unnonced An mcrease of 10 dBA u percerved as a doublmg of the no~se level, whereas a decrease of 10 dBA is perceived as a halvmg of the noise level Methodology In order to effechvely compaze esisnng notse em~ss~ons of traffic on varymg pavement types, the followmg envuonmental cntena was followed •: Locate exisung concrete and asphalt secuons of roadway that have surulaz roadway elevauon :• Locate secuons along Broadway Ihat do not have signalized mtersect~ons :• Locate secuons along Broadway that have tmmmal slope or grade. S Locate secaons along Broadway that have sim~laz speed and s~milar veh~de-m~x f^"` r..~ A field mvesagauon was conducted ro determme the best comparahve azeas for the pavement noise measurements and companson. The selected noise meastaement locanons have been mcluded on Figure 1 ~.,~e t Onsrte no~se readmgs were taken for approximately 10 nunutes at each locanon Traffic volumes, includmg vetucle mix were also taken at each locauon AII uaffic observat~ons were taken between 3 00 PM and 4 30 PM Results The results of the on-stte measurements have been mcluded m Table 1 There ~s no detectable d~fference m the on-srte measuremenu taken along Broadway at Sues I-3 There ~s a slight difference between these three s~tes and S~te 4 Tlus difference can hkely be attnbuted to the free-flow traffic condmons at Site 4 Site 1, 2 and 3 a11 had stop-and-go uaffic dunng the on-sue measuremenu Site 4 did not have stop-and-go vaffic cond~aons dunng the measurement The sites w~th the same traffic condi~ons but d~fferent pavement types (Srtes 1 and 2 compared to s~te 3) mdicate v~rtually ~denucal no~se condmons ex~st Table 1 On-Site MoniWring Results Monitoring Site Location Pavement T Time PM Decibel Level ( -dBA) 1 Broadwa & Can on As halt 3 10 68 3 2 Broadwa & Manne P.s halt 3 3~ 69 9 3 Broadwa & Pleasant Concrete 3.50 68 8 4 Broadwa & 17 Concrete 4 35 65 1 * Leq descnbes che mean nau leve{ d~nng tlx peak uaffic penod The stop-and-go traffic cond~aons at S~tes 1, 2, and 3 most l~kely result m an emphasis on ~dlmg and engme ~ noise from uaffic rather than ure/pavement no~se Therefoze, «~s d~fficult to ascena~n any d~fference m "" noise emiss~ons between the concrete and asphalt pavement alon~ this svetch of Broadway Research Numerous studtes have been performed m order to assess the difference m noise emissions from concrete vs asphalt roadways There aze three types of roadway surfaces that have been the general focus of analysis Portland Cement Concrete (PCC), dense-graded asphalt and open-graded asphalt Dense-gaded asphalt, m simple terms, is less porous than open-gradeA uphalt Further analysis haz also been done to compaze tex[ure types of PCC, mcludmg macrotextures, such as ~nmg, and m~crotextures, such as astro- turf drag Roadway hnmg aze the grooves created m PCC (concrete) highways to improve roadway draznage of ramwaur and reduce sladdmg. As~aturf drag is a more random surface texture that dces not penetrate deeply mto the PCC pavement surface hke nnmg, and is typ~cally uhl~zed for lower-speed, urban roadways Some of the smdies were mconclusive m deternunmg noise emiss~on dtfferences between the vanous surfaces and pavemen[ types However, some stud~es found [hat asphalt surfaces, PCC surfaces w~[h microtextures, and PCC surfaces with longitudmal aning aze all generally quteter than transversely uned PCC pavement, espec~ally m htgher-speed iughway cond~UOns When asphalt surfaces were compared w~th lona mdmally Uned PCC pavements or PCC pavements with an astro-mrf drag texture, there was Irtde or no perce~vable difference tn noise eaussion levels ~""4 :• The Federal Highway Admm~stravon dces not cons~der pavement type as an ophon for noue mmgauon `~ :• Literature research and mdustry pracuce has not reached consensus on which pavement type ~s the mos[ smtable based on no~s~related propemes However, there ~s more reseazch suppomng the not~on that asphalt surfaces are generally more qmet than transverse nned concrete surfaces When asphal[ surfaces were compared wrth longrtudmally vned PCC pavemenu or PCC pavements w~th an asvo- turf drag texture, there was l~ttle or no perceivable difference m no~se emission levels Please refer to the Research sect~on beg~mm~g on page 2 ~. Research mdicates tha[ umng generates a stgmficant change m pereerved noise levels. I.ongrtudmal unmg does not produce an audible whme and has sigmficanUy lower overall noise levels than transverse vnmg The change m percerved no~se levels typ~cally cecurs due [o frequency sh~frs assoc~ated w~th are no~se. Therefore, if the concrete pavement is uned, a difference m noise levels, typ~cally tugher, could occur Tmmg is not cucrendy planned for the Broadway Ruonstrucuon Pro~ect The pavemen[ would recerve an asho-turf drag fitush similaz to the port~ons of Broadway (Regent to Umversrty) reconstructed to concrete pavement m the early 1990s o As was mennoned above, no~se em~ss~ons from traffic on varymg pavement types may change over hme It should be noted that current modelmg techmques aze unable to accoun[ for or accurately pred~ct changes m no~se eicussions due to pavement transformauon over nme References 1. Ardam, Ahmad and Outcalt, Wi1Lam, PCCP Textunng Methods - Repon No CDOT-DTD-R-00-I (Colorado Depamnent of Transportauon, 2000) ~ 2. Highway Traffic Noue Artalysu and Abatement- Pol~cy and Gurdance (Federal Htghway Admm~stranon, 1995) 3. Jaeckel, JR, et al, Noese Issues of Concrete-Pavement Textunng (Transportadon Reseazch Board, 2000) 4 Kuemmel, DA, et al, /mpacts Related to Pavement Texture Selecnon (HN1'B Corporaaon, Mazquette Umvers~ty, Wisconsm Department of Transportauon, 1997) 5 Kuemmel, DA, et al, Noue and Texture on PCC Pavements - Results of a Mult~-Stare Study (Mazquette Umversity, Wisconsm Department of Transportauon, 2000) 6. Volpe Nauonal Transportadon Systems Center, Acousucs Facil~ty, Development of Nat~onal Reference Energy Mean Emrssaon Levels for the FHWA Traf~"ic Noise Model (FHWA TNM), Versmn 1 0(Federal Highway Adm~mstrat~on, U S Departmen[ of Transporta~on, November 1995) 7. Wayson, Roger, Relahonship Between Pavement Surface Texture and Htghway Tra~f"ic Noue NCHRP Synthesis 268 (Transportation Reseazch Boazd, 1998) NDENI fDl\VOLIUOBS~_Transportauon\070363\workmg~anWo~u_asphaltvsconccete_final_090401 doc ~