X\L- 76-XX-22

URBAN DESIGN AND PUBLIC EXPOSURE

TO CARBON MONOXIDE

ENVIRONMENTAL POLLUTANTS and the URBAN ECONOMY

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A\L- 76-XX- 22

URBAN DESIGN AND PUBLIC EXPOSURETO CARBON MONOXIDE

Danilo J. SantiniArgonne National Laboratory

October 1976

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ENVIRONMENTAL POLLUTANTS and the URBAN ECONOMY

Argonne National LaboratoryEnergy and Environmental Systems Division

The University of ChicagoCenter for Urban Studies

This wt'rk was partially supported by the Natioisal Scince Foundation. Rescaich Applied to National Needs(RANNI.Cntract Nos AG33.2 and GI .2989A2. lioweve. any opinions. findings. conclusions. o recommenda-tons e presed herein are those of the authors and do not nct uArdy reflect the views of NSF

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CONTENTS

Page

INTRODUCTION 5

LOCATIONS WITH THE HIGHEST CO CONCENTRATIONS . . . 5

LOCATIONS REQUIRING PROTECTION OF THE PUBLIC 6

METHODS OF REDUCING EXPOSURE RISK . . . 6

USE OF PHYSICAL DESIGN TO REDUCE EXPOSURE RISK . . . . 8

TYPICAL BUILDINGS IN AREAS OF HIGH CO CONCENTRATIONS 9

FACTORS AFFECTING COSTS AND BENEFITS. I I

POLICY IMPLICATIONS . . . . . . . . . . .I I

3

URBAN I-SIGN AND PUBLIC EXPOSURE TO CARBON MONOXIDE

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Their pollutant carbon ionoside i( Op is produced by incomplete combustionin motor svhicles. space heating. industrial prosesses. and incineration. Currentresearch indicates that higher density residential developments. because they lead toreduced demand for luckfor home heating and transportation, tend to lower totalcarbon mono, de emissinIs. Hlowese,. it is in these same areas that concentrationsof CO are the highest because of the density of emitters. Since carbon monoxidestandards specify maximum allowable concentrations rather than emissions, theytend to deter further development in locations where concentrations are alreadyhigh i.e.. high densit, downtown areas. This deterrent effect coa.tnbutes to greatertotal emissions of carbon monoxide. hence, it may be desirable to devise a means ofcentrolling the public's risk of exposure to high CO levels in downtown areaswithout deterring new center cit) residential development.

In protecting the public from the risk of exposure to damaging levels of carbonmonoxide. two approaches are possible: the pollutant's concentration may belowered b) traffic management measures or the public's rate of exposure may bereduced through urban design features. The present emphasis on traffic managementstresses improving the tlow and reducing the level of traffic - goals that areextremely costly to achieve in downtown areas. This paper examines ways to reducerisk of exposure by the physical design of new downtown residential developments.The concept is not a nosel ore. having been successfully implemented in industry topros ide occupational health and safet).

In order to use physical design to protect the public from exposure to excessivecarbon monoxide levels. an architect or planner needs to be able to answer thefollowing questions:

" Where on a specific site will CO concentrations be the highest'" At what t) pes of locations should the public be protected'" What design altermiatises are asalable to provide this protection'

These questions are addressed in the following sections.

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Current research into arhon monoxide emissions and concentrations indicatesthat siotationis of carbon monoxide standards are most often caused by queuing ofsehicles at intersections or other impedinwnts to traffic how. This occurs becauseeach vehicle emits carbon monoxide laster when idling or traveling at low speed. andfor a given emission rate 4mg mun per vehicle. concentrations buik up at locationssuch as stoplights where vehicles are gationar) .

Higher (0 levels also occur when the pollutant is trapped in troughs or tunnelswhere normal wind currents cannot disperse it In a New York City study. exampleswere found wh:re deep cut hidhwa) s. urban canyons. tunnels, and air rightsconstruction were associated with violations of the carbon monoxide standard even

w' 1 hcn tratfi , a~ IfcclI IIio luig. I lt ci'c. 11 st uiton'. ' herer .a ar Ir.I :Iitsi is geod.iafron nIonosdc t cinelritnfsls l Isul' r j;'rapidl) itl dtlt s I' Iru nt ilt Cilisssinsurct ( ta qucntl'. 'in .l t .al iIt 'l.'1 b thlt p rie' I a t rat1ak tIo .and.Jrbon iIti3noidC JIpIrs.J thJrf. tCfsti I LIuI.ItIttI that iiiid-hlt' I J.f1 iitefiiorlocations aMil consistent uI) .c s lo't.r tiron ,non ue ItIC It'cis thanI t hos ncarintcrs4.t oI1'..

An) location which as suabiet to and I nsiolation of a ( () standard k all) Iruliressome form of crposurc risk control. Snkc the Juratoti ol crp.suarC I .as "tportantas the onccntrationt kcl to hinh a person is crposed. a dIIesigi obit-tasc sould tto insure that people spend the naJurt) ul their t iu '.e hcrc bse.nnitrations artbelow the nusamumn a..cplablc level.

The L'. S. I- its ironmental Protction Agnctt.' ii PA im'li tly re..mnaIcs thisobjcsc ni n its definition of rcasnabl rceplor sits

Reasonable receptor or c potsure uts shall mncan sw. I lo atiuIiswhere people iight reasonabl) cipowd o r time crodsconsistent wist the national amtbcnt air quakt standards o thepolkliant specsifed .

(k'upationt fsreuirilg 1soC CcrIpoure In ( () as a pertr:1%a%ac Igicrion Itrafiidirection. lab dn'i.ng. etc.I arc sub)ce to different standards. b ids .arc establishedby the Ottupational Saflt) .and Hlcalth Akt tOSlIAs.

Most rccptor sites hA10h .arc deemed unrcausnablc arc places whcre people mightbe on a roadway but not in an autoimobilc Pl'urtions .of parking lots bcrc thegeneral publi I not likel) to baste aces contmuousl) ac .also unrcasonahkreceptor sites. The IPA applies an as'rage risk 5rilerson to persons wakIing onsidewalks. resulting in an int se tion to ntcrstlion Jscr.gng proi.edurc Ihispermits udewalks to be built in areas where the standard is siolated a 1..ntrsections as long as mnost of ti- hil) sidewalk trip as i1 areas where (Y)concentrations arc acteptabl) low

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For a gasen rate of ceuisuons. distance trom the source is the most clectise wa)of reducing csposure rates i urthermore. scrtial distant tr.111 th rll fce c em 1.tobe a nore refctcisc means of aoading high constntrations than downwindhorutontal distance. as illustrated in able I

Some idea of the distances uetssvr) 1n reduce urrcnit crposiirC rates toacceptable levels ma be obtained h) camiing .aitual urban carbon onouadeconcentrations. During the 1'74.75 monitoring year for the ('it) of (hicapo. thwost "cond highest" (C sal-.c Ithe rcgultiaon allows for cposure to onevsolation of the standard per )eaI as 1'.7 mg m' average t oser an eight hourperiod. If this salute is di asded into the eight hour legal limit ot 10 mg m'. theconcentration reduction factor nec-ry to meet the standard is found to be 0.507.Asuming that the area in question reprewnts a t)pic.al dlt) blosk 1 c.. no urbancanyons or similar impediments to (() dispersion then a sertical distance from thislocation of .15 t or a downwimd horitntal distance o1 S( It would provide the

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I AtIII I I iuaj%ta nt I)itans i tim Read I-dgc t A,.hcsc Ieeuted ('n.entrataon Rcdustaun*

I)1recqj 1 efnl lii enRcdu..ign I I a.te 'D ( 74 57 0 44 0.4 0.27

Vet1 ial I)i 'afl.c..c1..ara 1iti iI) .I 1 40 S0 t0

lies /a ental I I e' MwiirtdIintao..c Nc s iar it i 4 :11 42 "1 110 170

*ItaieJ nreferenl e entrAiieeI 1uares ruhIdled In h i er'a.>iiwagn-rtal Irnpuit /andbaae f rlIghsrseva Sui rns I I I) #eehIee k I cl+.-n and I J IlIabrggr .Argenne National

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gnetr ;'ulia ith .31 aem o.iaw tm 5II .1.pt.abik JlSaon in erms ot carboamoaanoud tanda11)hrd v H> gpre'raiug .a 1amaI.ar JaLLtIation for the as-crage Chicagoarlum: m,"ansoude monitor. onm I 1ndf tl.at .1 serti.al >r hortont.Jl dasl.anc of 20 Itwools d sI8I . It should emp13'Ih.%/.d hIer Ihat while thew monitor% are not placed

at the edge% of road.. th l tcnI arc nw.ar oume tat 1Chiago' more hiea.ly trailled.Iettl. ( onb tlutt . th di %t.ans. inmpl b thed + . t oh c jIow ulataon arc presented

for illu.'trat ie 'pur;p)ows onIlPi'tuljtion cpoosurc to .arbo mnonoude is . Iso suhbt.ntall) rcducd when

people .ar eindoor.. an d.atj pnro) a ' the. C .h) h .s o k)tpartme nt of I mn.'ron-m1cl Ctuiontrsl. a re grwoJt n modde l was discloped w hah I i.' hImatcf (C '()oncvntrataon

ansade tih ground loor entrain a of a building . a I incton of the outdoor COconcentrjt ion. skctcd estmajte l a thew relatonhip. arc prawncad aI i.abl 2.

attla: I mis'al .'that ,on.atrtiaon% Insade thI tl I)pia building ..' ground esedSaIl t Ir th.an Ih .a Ihumum an ;tjahle .alke'a llen outdoor on0enlfltfrtil'n are up

to t wiac th eight hour t.nd.ard. in ta t. Iable 2 how% that CO ionciiratonswould best mii ronmentall) .5 t.l an.Id the ntranc of a building adjl.cent to anoutdoor arcJ ilth( C )onntr.tnat on5'.ttcrnt% luialnt to th ue wu:t monitored in

(hIca-o m I1)74-75. Ith roegwnsaoa namodl that gtnerated the "sttmatcs in Table 2mihtdes dat a for mjait ioulder build ings. w 1hi. h stl> arc helad to hat higher COk'dis than anw building sn nwhii entral hPiating oolang s) >em" s are used an

...)njiiiktiantI *ith uppr floor .ar miles and tcerior %urljsos designed for lowamithnt .ar intaltr.ation. If building g ntra:c arc pLaced .jwa) from CO sources.thwre should ht little problem with c%:si% e rpourc in the striiturc. an naew ofIhe aomit'ctftrat)n 'io/tii a) monitored in ls ( hip.ago Jrt..

I AIl1 I . Iaindeo'.el ' () ( t.,ati tta. at1 .. J I i 'n a Ita (d)u .de.' ( ) ' .cn ntSl.'n

(hut dao (CO('onrentratian In gn' I 2 0 tr 100 14 0 ' 0 22.0

-slaanaled Indo C)O('oncentrsat.n igj mn'1 2 43 0 '' . 2(010.0

*A L1a 1niennaataaons. The ind.,, (C) Olevels. an c.ead thine outdo or. because 1f uokingand orI uel .. eimhuaanim I11 h st ing

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L'%' uf Phi i rweal kI)eg's it) Reduct v uipuur' RiAIt is apparent from the IPA definition of reasonable receptors described earlier

that planning to meet U PA requirements can solve some exposure problems bymanipulating the relationships bet-een outdoor public space and spatial variation InCO concentrations.

For example. although sidewalks are traditionally constructed next to roadways.this certainly is not necessary. If they were to be moved away from roads in generaland intersections in particular, the exposure rates of pedestrians would be reduced.It is possible to design sidewalks that will reduce the time of exposure at anintersection b) the use of geometrical properties. At a uniformly congestedintersection with random wind patterns, sidewalks oriented at 450 from theroadways minimize pedestrian CO exposure near the inter-ection. Away from thestreets. sidewalks might resume a direction parallel to that of the roads. Givendifferent relative congestion and wind directions. the optimum angle for thesidewalks would vary. Two sidewalk design options are illustrated in Fig. 1.

Another use of the sidewalks is for public transit stops at intersections, which aredesirable from an operational standpoint since buses have to stop at intersectionsanyway. However. environmentally, a mid-block transit stop, out of the movinglanes of traffic, is more desirable when intersections are particularly bad.

A possibly unat:ractzve way to prevent the public from using open spaces that arelikely to have high levels of CO is to place fences around those areas. Moreaesthetically pleasing solutions, especially for a boundary between roads andresidential developments, may be to (I) plant the area with appropriate shrubbery or(2) build earthen mounds covered with planting. The earthen mound designalternative can also reduce ground level noise within the area and provide a morepleasing ground level view for persons looking toward the stree:.

ROAD A -- - ROAD A -

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CASE A CASE OR CASE C

RANDOM WIND RANDOM WIND PREVAILING WINDEQUAL ROAD VOLUMES ROAD A GREATER EQUAL ROAD

VOLUME VOLUMES

Fig I. CO F piure Reducing Sidewalk Design

Fenc: s can present short-ut pedestrian routes across ground level parking lots.Vehicle access points into parking lots or garages may be separated from pedestriantraffic by eliminating sidewalks at the %chicular entrance and placing sidewalks andpedestrian entrances at edges of the parking Ias.hty which are removed from thestreet. Within dhe parking facility itself pedestriai flow should he separate fromvehicular flow. and the pedestrian :.',d ehicular entrances and exits should bedistinct, with vehicular p isages designed to discourage pedestrian us:.

The parking lot entrance or exit. since it is a location where a queue ofautomobiles may build up. is equivalent to ai intersection. A parking facility servinga particular building will hale peak parkmig volume at the same time as peakpedestrian volume. since many pedestrian entrants to a building are merely peoplewho recently left their parked cars. I herelore. when parking facilities serve aparticular building. it is enmironmentall% desirable to separate the vehicular parkingentrance from the pedestrian building entrance.

When all other hings are equal. tne property lies of hospitals, rest homes, andplaygrounds should he further removed from areas of high CO concentration thanthose of other facilities. [he populations of hospitals and rest homes are inherentlymore susceptible to the deleterious effects of carbon monoxide and playgroundexercise increases children's uptake oh (0.

Other suggestions can he made with respect to street and building configurationand parking facility location. F irst. when internal roads are placed at the outsideboundary of a site adjacent to high %olume road ia s. then these rather low volumestreets act as buflers trons high (( concentrations at the border of the site. Second.construction ol parking facilities in the lower floors of a high rise residentialstructure increases vertical distance beti;een high CO conce.'trations and living units.Finally. parking garages placed .it intersections prevent ground level public use ofsuch locations. public recreational facilities on the root of this type of parkinggarage would be one way of maintaining desired environmentally acceptable publicspace.

T-pi al Buidings in .-Ireas if lmith ('0 ( oe cniranui' s

Carbon monoxide is likely to be a problem in areas close to high volume. stop andgo traffic. Further, the extra traffic created by commercial and business activitygenerally leads to higher carbon monoxide levels. Usually sites with suchcharacteristics will be lo'.ated near the business core of a city or town, where netresidential densities most often are consrderably higher than in a city's purelyresidential areas. The type of residential building commonly found in suchenvironments i.e.. tie multi-floor mid- and high-rise building is desirable fromthe point of view of reducing CO exposure.

Multi-story living in the vicinity of heavy traffic volume has several virtues. First,upper story dwelling units themselves have the advantage of vertical distance fromthe source of pollution which, as mentioned, is even more effective than horizontaldistance. Second. in upper floor dwelling units., residents do not use the air spaceimmediately adjace, t to the unit for recreational purposes. Third. in multi-storybuildings, it is possible (and common) to install air intakes for the building at upperlevels for central heating and/or air conditioning. Finally. the entrance of amulti-story building may be designed to be a reasonable distance from sources ofcarbon monoxide. These desirable properties of multi-story buildings exist onlywhen land coverage by buildings is not complete. If multi-story buildings arc used at

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all locations along a roadway. these sirtues are eliminated because an urban canyoneitect is created in which carbon iioonomide emissions are trapped. Reasonablyspaced buildings are necessary for good air circulation and carbon monoxidedispersal

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I his paper has suggested th.it phy sisal design can he employed to protect thepubli I rom .arbn imonoxide concentrations in the case of residential developmentsclose to high solume. stop and go traill An important question is whether thesuggestions made here are mnexpensise and otherwise desirable methods of designingsuch residential deselopnents. I his question is best answered on an individualdeselopment-h -deselopnent basis. Iloweser. the suggestions made here do notrequire extraordinary innosations in designs. In fact. examples of e.ch of thesuggestions base been tound :o 'eist in Chicago and its suburbs. and these designalternatives dad not arise from considerations of carbon monoxide concentrations.(onsequently . it is reasonable to assert that some of the suggested design alternativesare likely to octuor in a dos ntow n I city or suburban) development even if exposureto carbon monoxide is not considered. Where high-rise or mid-rise buildings andparking garages are to he used Iof .a particular deselopment. then the suggestionsmade here amount only to careful selection of the locations of sidewalks, parkingfacilities. access roads, and buildings.

When the alternative to physical design is traitic manipulation. there will be manycases in hich phy sical design will be the more economical means of lowering publicexposure to CO. Another advantage or phy sical design over traffic ccitrol is that themethod of meeting the objective is completel internal :o the developer. It is notnecessary to convince the public bodies responsible for road design to adopt trafficcontrol measures that will affect more persons outside the site than within. Evenwher, traffic control is a cost-beneficial solution on theoretical grounds. it may beditficult to operationally effect the transfer of benefits from the residents of the siteto the drivers and passengers who pass by the site or who are forced to take analternative route

Ai//( Implu attuun

This discussion has concerned a neglected and potentially cost-effective approachfor complying with carbon monoxide air quality regulations. The discussion here hasbeen neceswirily briei. and fails short of providing all the knowledge needed for thesite planner or architect to decide when the techniques suggested are useful and towhat extent they could be applied. If the approach suggested here were to beaccepted as a complement to CO emissions reduction through local traffic control.then design handbooks could readily be developed for use by the professional designconinuinity.

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-or further informationstudy described in thisplease contact:

on thereport.

Dr. A. S. CohenArgonne National Laboratory

Energy and Environmental Systems Division9700 South C-ss AvenueArgonne, Illinois 10439

or

Prof. G. S. TolleyThe University of ChicagoDepartment of Economics

1 126 East 59th StreetChicago, Illinois 60637