Downloaded from: Version: Accepted Version Publisher: Inderscience DOI:

Transcription

1 Govans Elefheros (2015)Evaluaon of he Clean Ar Wors on acual ozone concenraons: a case sudy n Norh Carolna. Inernaonal Journal of Envronmenal Technology and Managemen 18 (5/6). pp ISSN Downloaded from: hp://e-space.mmu.ac.u/620958/ Verson: Acceped Verson Publsher: Inderscence DOI: hps://do.org/ /ijetm Please ce he publshed verson hp://e-space.mmu.ac.u

2 Evaluaon of he Clean Ar Wors on acual ozone concenraons: A Case sudy n Norh Carolna Elefheros Govans Mare Slodowsa-Cure Prncpal Research Invesgaor-Fellow Unversy of Verona Deparmen of Economcs Va dell'arglere Ialy and Royal Holloway Unversy of London Deparmen of Economcs TW20 0EX Egham Surrey England Emal: govans95@gmal.com and Elefheros.Govans.2010@lve.rhul.ac.u Absrac Ths sudy examnes he effecveness of he Clean Ar Wors n he sae of Norh Carolna on ozone concenraon levels. Clean Ar Wors s a volunary whch educaes people abou he negave effecs of ar polluon on healh. The conrbuon of hs sudy s ha examnes hree effecs: The effecveness of he Clean Ar Wors n he Charloe Area of Norh Carolna Sae and wheher ozone smog alers are more effecve under hs. Fnally he effecs on ozone levels comng from he change n he warnng hreshold from 80 parcles per bllon (ppb) o 75 ppb whch oo place n 2008 are esablshed. In all cases we fnd reducon n ground-level ozone levels and mprovemen of he ar qualy n he reamen group where he Clean Ar Wors s mplemened 1. Keywords: Ar Qualy; Clean Ar Wors; Envronmenal Technology and Managemen; Quadruple Dfferences-n-Dfferences; Ozone concenraons; Smog alers; Volunary Programs 1 We would le o han Mrs. Adrenne Wooen Meeorologs n Sae Clmae Offce of Norh Carolna for provdng meeorologcal daa and Mr. Cary D. Genry Sr. Envronmenal Specals for provdng AQI forecass n Trad regon hrough

3 1. Inroducon Ar polluon has long been recognzed as a negave exernaly. Mang regulaons concernng ozone s an area of ncreasng mporance. Envronmenal polcy maers around he world ncreasngly rely on volunary s o mprove envronmenal qualy (Cuer and Nedell 2009). For example More and Nedell (2011) provde drec evdence ha people respond o nformaon abou ar qualy. The am of hs sudy s o examne he effecveness of he Clean Ar Wors along wh smog alers. The second am s o explore wheher he ozone smog alers are more effecve under he Clean Ar Wors. The hrd am s o esablsh he mpac of he change n he ozone warnng hreshold sandard ssued by he Envronmenal Proecon Agency (EPA) from 80 ppb o 75 ppb whch oo place n In order o denfy hose effecs a quadruple Dfferences (DDDD) esmaor s appled. The resuls show he ar qualy has been mproved n he reamen group wh he mplemenaon of he Clean Ar Wors reducng he dfference n ozone concenraon levels by 1.27 ppb. In addon he smog alers are effecve under he regme where he above-menoned dfference becomes 1.8 ppb. Furhermore he dfferences of ozone levels beween he reamen and conrol groups are addonally decreased afer he change n hreshold by around 1.50 ppb when he s mplemened and s assocaed wh smog alers. As such nformaon on ar polluon does no seem o sgnfcanly reduce polluon level unless a le Clean Ar Wor whch faclaes seps reducng polluon s n place. The srucure of he paper s he followng: In secon 2 he leraure revew s provded. Secon 3 descrbes he envronmenal polcy and he Clean Ar Wors proec whle secon 4 revews he mehodology of he model used n hs sudy. Secon 5 presens he daa and he research sample used n he esmaons whle n secon 6 he emprcal fndngs are repored. In he las secon he general conclusons of he emprcal fndngs are dscussed. 2

4 2. Leraure revew Ths secon presens and dscuses prevous leraure relaed o he curren sudy. These sudes examne he effecs of publc advsory s on raffc. Smlarly Clean Ar Wors proec encourages ndvduals o follow pracses ha reduce ar polluon such as publc rans and carpoolng whch affec he raffc paern and resulng n changes of he ozone concenraon levels. One of he publc advsory s explored n prevous sudes s he Spare he Ar (STA). Spare he Ar was esablshed by he Bay Area Ar Qualy Managemen Dsrc n order o educae Bay Area resdens abou ar polluon and o encourage hem o change her behavour o mprove ar qualy. As par of he Spare he Ar he resdens are ased o reduce polluon by mang clean ar choces every day; from walng and bng more ofen o reducng energy consumpon a home. Spare he Ar days are declared for days n whch levels of ground-level ozone are predced o exceed he EPA s federal healh-based sandard: he ar qualy ndex (AQI) over 100. Moreover on a Spare he Ar day Bay Area parcpans are ased hrough rado and elevson announcemens o leave her cars a home and o ry an alernave commue. Schreffler (2003) used daa over wo summer ozone seasons n Sacrameno allowng researchers o compare he ravel behavour of he same ndvduals on boh Spare he Ar and regular summer days and of Spare he Ar parcpans and non-parcpans. More specfcally he parcpans s a group of drvers who sad hey purposely reduced rps because of Spare he Ar whle non-parcpan s a conrol group of drvers who dd no respond o he STA message. Schreffler (2003) found a sascally sgnfcan 4.8 per cen reducon n rps. The 4.8 per cen reducon n rps resuled n an emsson reducon of 1.04 ons of ozone precursors. The precursors n hs sudy are he nrogen oxdes (NOX) and volale organc compounds (VOCs). Ths s smlar o Clean Ar Wors examned n hs sudy. Ozone warnng announcemens encourage people o reduce drvng or o use publc rans and varous nds of rdesharng such as carpool and vanpool or o encourage eleworng. 3

5 A smlar wor o he curren sudy s by Cuer and Nedell (2009) who examned he effecs of Spare he Ar advsory n he San Francsco bay area usng a Regresson Dsconnuy (RD) desgn. More specfcally hey compare he bay area where he Spare he Ar (STA) aler s ssued and he Souh Coas area where he STA s no appled. Cuer and Nedell (2009) esmae a regresson dsconnuy approach usng a sample of observaons whn 2 and 1 ppb of he lm for a STA call and hey show a sascally sgnfcan drop n vehcle usage of beween 2000 and 2300 per day. On he oher hand Cummngs and Waler (2000) examned a smlar volunary n he Alana meropolan area on hourly raffc volumes and found sascally nsgnfcan effecs. Generally he prevous sudes examned he effecveness of publc advsory s on raffc volume and rdershp paern; bu he change n he ozone warnng hreshold has no been explored. Thus he curren sudy conrbues o he prevous leraure by examnng he effecveness of he Clean Ar Wors volunary assocaed wh smog alers and he change n he hreshold. In addon he weaher daa have been negleced n he prevous sudes wh he excepon of he sudy by Welch e al. (2005) who use varous weaher condons such as emperaure days wh lgh and heavy ran and exreme weaher ncludng hundersorms and oher exreme condons. I s crucal o conrol for weaher condons for he followng reasons: Frsly he weaher condons affec he ozone formaon and nfluence he raffc paern and flow. Ground level ozone s formed n he ar by he phoochemcal reacon of sunlgh hgh emperaure and nrogen oxdes (NOx) faclaed by a varey of volale organc compounds (VOCs) whch are phoo-chemcally reacve hydrocarbons (Cruzen 1974; Derwen e al. 2003; Pudasanee e al. 2006). In addon wnd speed and drecon are mporan facors for ozone as prevous researches found relaonshp beween wnd drecon and speed and ground level ozone (Agudelo-Casaneda e al. 2013; Fgueredo e al. 2013). More specfcally wnd speed cleans he ar n an area and conrbues o how qucly polluans are carred away from her orgnal source. 4

6 3. Envronmenal Polcy 3.1 Smog Aler and Ozone Forecass Ar qualy forecass measured n par per bllon (ppb) are provded by he EPA whch ses he Naonal Amben Ar Qualy Sandards (NAAQS). The Ar Qualy Index ranges from 0 o 500. From 1997 he naonal sandard was se up a 80 ppb correspondng o 111 of he revsed AQI. In 2008 hs sandard was reduced o 75 ppb correspondng o 100 of he AQI. EPA revsed he hreshold level o provde ncreased proecon for chldren and oher a rs populaons agans an array of ground-level ozone relaed adverse healh effecs (Envronmenal Proecon Agency 2008). Ozone forecas s dsrbued and s avalable o he publc hrough local meda (elevson rado and newspaper). A smog aler s ssued n he case where he forecas passes he hreshold 80 ppb and 75 ppb for perods and respecvely. In ha case he Norh Carolna Ar Awareness Program ulzes a wde range of web and meda oules o broadcas he ozone forecass o he general publc and her mpac on healh. 3.2 Clean Ar Wors Program Clean Ar Wors launched n sprng of 2006 and s a proec of he Regonal Ar Qualy Board n collaboraon wh he Cy of Charloe Meclenburg Couny Charloe Area Trans Sysem (CATS) he Charloe Chamber of Commerce he Cenralna Councl of Governmens and he Caawba Regonal Councl of Governmens. The parners of Clean Ar Wors proec ry o educae employees abou he effecs of ar polluon on publc healh and o provde a low or no cos ransporaon benef o employees. Also hs encourages and educaes employers o follow varous polces such as he use of low emsson or alernavely fueled vehcles and mplemenng energy conservaon plans. 5

7 6 4. Mehodology 4.1 Quadruple Dfferences-n-Dfferences Model The model examned n hs sudy s a quadruple DDDD whch has he followng form: z l W hreshold warnng rea hreshold warnng hreshold rea warnng rea hreshold warnng hreshold warnng hreshold rea warnng rea rea hreshold warnng rea ozone (1) The dependen varable ozone sands for acual ozone levels n ar monorng saon locaed n couny n forecasng zone-regon and n me. Varable rea denoes wheher he counes belong o he reamen or conrol group and capures aggregae facors ha would cause changes n ozone levels even n he absence of he mplemenaon such as he Grea Recesson. Varable aes value 1 snce he Clean Ar Wors has been mplemened n 1 s March of 2006 and afer and 0 oherwse and capures possble dfferences beween he reamen and conrol groups pror o he mplemenaon. Warnng s a dummy varable ang value 1 wheher here s a smog aler and 0 oherwse whle hreshold denoes he change of smog aler hreshold from 80 ppb o 75 ppb. I aes value 1 for 27 h May of 2008 and afer and 0 oherwse. A he same me he model conrols for he day of he wee monh year counes ozone regons and weaher daa (W) such as emperaure wnd speed wnd drecon and solar radaon. Se (μ) ncludes dummy varables for he monorng saons (l) s a se ncludng couny dummes (z) expresses he ozone forecasng zones-regons fxed effecs and θ s a se of me-fxed effecs. Fnally ε expresses he error erm. Clusered ozone monorng ses are consdered for robus sandard errors. The dfferences-ndfferences mehod can be mplemened accordng o able 2 (Angrs and Psche 2008 p ):

8 (Inser able 1 around here) Varable y s he oucome-acual concenraon ozone levels expressed ppb n hs case- whle g and denoe he group and me respecvely. More specfcally he dummy varable rea capured by he coeffcen β5 shows possble dfferences n ozone levels beween he reamen and conrol groups pror o polcy change (before he mplemenaon of he Clean Ar Wors ) and afer. The normal dfference s defned as (yb1- ya1) whch s he dfference of he average ozone levels beween he reamen and conrol group before he mplemenaon of he. The expresson (yb2- ya2) ndcaes he normal dfference plus he reamen effec of he mplemenaon. The dfference-n-dfferences esmae s shown n able 2 and s β5 =(yb2- yb1)- (ya2- ya1). Therefore he essenal dea of he double DID) esmaor s o compare samples of he reaed counes and conrol counes before and afer he nervenon ( Clean Ar Wors ). The DD calculaes he dfference beween he afer and before values of he mean oucomes (ozone levels) for each of he reamen and conrol group. Then he dfference beween hese wo mean dfferences s he mpac esmae of he nervenon. In a smlar fashon he rple DDD esmaor (expressed by he coeffcen β11) and he quadruple DDDD esmaor (expressed by he coeffcen β14) are defned. In fgure 1 a hypohecal DID plo s presened as an example. More specfcally before he polcy boh groups face he same average rend whle afer he polcy he rend change n he reamen group as he effecs on he oucome ump downwards represened by he dashed lne. The grey lne shows ha he average effec would be he same n boh groups wh he absence of he polcy or n he case ha he polcy would no be sgnfcan. Thus n plan words DID sraegy s based on comparng four groups. These groups are he reaed before he reamen or polcy mplemenaon and s defned as he pre-reamen reaed he nonreaed or he conrol group n he perod before he reamen occurs o he reaed whch s he prereamen non-reaed or conrol. The hrd group s he non-reaed or conrol n he curren perod 7

9 whch s he pos-reamen non-reaed. Fnally he las group s he one whch already receved he reamen or where he polcy (Clean Ar wors n hs case) s mplemened and s defned as he pos-reamen reaed. Therefore he dea of hs emprcal sraegy s ha he average changes of he oucome varable for he conrol group over me are added o he average level of he oucome varable for he reaed group pror he mplemenaon of he polcy o oban he average oucome ha he reaed group would have experenced f had no been subec o he polcy or he reamen. (Inser fgure 1 around here) In addon anoher advanage of hs model s ha conrols for addonal facors such as for weaher condons. Thus hs secon presened he man framewor of he DID sraegy along wh s advanages over smple sascal analyss such as smple averages and sandard devaons of he acual and predced ozone levels before and afer he mplemenaon. 4.2 Tes of he Quadruple DDDD Model Valdy In hs secon he mehodology followed for esng he valdy of he DID model s dscussed. Then n he resuls secon he robusness checs are presened. More specfcally he common rend or parallel growh-rend assumpon s examned. Ths assumpon saes ha he dfferences n he expeced poenal non-reamen oucomes over me are unrelaed o belongng o he reaed or conrol group n he pos-reamen perod. Ths s he ey assumpon of he DID approach. I mples ha f he reaed had no been subeced o he reamen boh reamen and conrol groups would have experenced he same me rends. Moreover DID conrols for oher facors affecng oucome 8

10 9 n boh groups around he same me such as he grea recesson whch affeced boh groups and s no a local effec. In order o es he parallel or common rend assumpon s o place placebo dummes before he reamen. More precsely he DID s esmaed assumng ha he Clean Ar Wors proec oo place before More specfcally we assume ha he polcy oo place n 2004 nsead of 2006 and he basc DD model s esmaed usng daa from : z l W rea rea ozone (2) The reason why n model (2) only he double DID s examned s because he only dfference beween he conrol and reaed group s he mplemenaon of he Clean Ar Wors. On he oher hand he smog aler advsory and he change of hreshold are appled n boh groups as has been dscussed n secon 4.1. Thus s only necessary o es he valdy of he double DID whch refers o he effecveness of he Clean Ar Wors examned and whch dfferenaes he reamen and conrol groups. The second es of he DID valdy s o nclude a se of lags and leads no he basc DID model (2). Includng leads no he DID model s a way o analyse pre-rends whle lags can be ncluded n order o analyse wheher he reamen effec changes over me afer he mplemenaon of he Clean Ar Wors. Regresson (2) s wren as: q p p p m p p p z l W D D rea ozone (3) Regresson (3) s esng for causaly n he framewor of Granger (1969) and D s defned as he neracon erm rea defned n regressons (1) and (2). More specfcally Granger

11 causaly es s a chec on wheher pas D predcs he ozone whle fuure D does no condonal on couny and year effecs. The sums on he rgh hand sde of equaon (4) allow for m lags (β-1 β-2...β-m) defnng he pos-reamen effecs and q leads ((β+1 β+2...β+q) defnng he ancpaory effecs (Angrs and Psche 2008 p ). 5. Daa The acual ozone concenraons are measured a couny level whle he ozone forecass are assgned on regons group of counes. The counes reaed are Lncoln Meclenburg Rowan and Unon n Charloe Area whle he counes used as conrol group are he followng: Forsyh Rocngham and Gulford Counes n Trad area Ralegh Couny n Trangle area Cumberland Couny n Fayeevlle area Buncombe Couny n Ashevlle area and Caldwell Couny n Hcory area. One of he reasons for choosng he reaed and non-reaed counes s ha all of hem are consdered as non-aanmen areas. More precsely he Clean Ar Ac and Amendmens of 1990 defnes a non-aanmen area as a localy where ozone levels perssenly exceed Naonal Amben Ar Qualy Sandards as has been dscussed n secon 3. The daa for forecasng ozone concenraons have been rereved from he Norh Carolna Deparmen of Envronmen and Naural Resources (hp://daq.sae.nc.us). Ozone forecass are made daly durng he ozone forecas season from May 1 s hrough Sepember 30 h. The meeorologcal daa have been ndly provded by he Sae Clmae Offce of Norh Carolna ( The weaher daa used n he esmaes are he average daly emperaure wnd speed wnd drecon and solar radaon. The daa are based on daly frequency and he perod examned s In able 2 he summary sascs for acual ozone concenraons are repored. (Inser able 2 around here) 10

12 The ozone levels have been reduced also n he conrol area for he followng reasons: Frsly by reducng he hreshold by 5 ppb n 2008 a smlar reducon on he ozone levels s expeced. Ths s because he new ar qualy sandards defned by he change of he warnng hreshold mply srcer and gher regulaons assocaed wh fee penales for volaon of hese sandards. Thus he local governmens of he counes are responsble o ae addonal measures and polces o mprove he ar qualy and avod hese coss from he fee penales. However an addonal reducon n ozone levels s observed n he reamen group. The reason s ha he reaed counes benef from he Clean Ar Wors as has been dscussed n he prevous secon. 6. Emprcal resuls In hs secon he quadruple DDDD esmaes are presened. As has been dscussed n he prevous secons he purpose of applyng he quadruple DDDD s o examne he effecveness of he Clean Ar Wors Proec wheher or no smog alers are sgnfcan under he regme and o esablsh he effecs of he change n hreshold by EPA from 80 ppb o 75 ppb. The esmaed regresson (1) s presened n able 3. The frs coeffcen of neres s he coeffcen β5. Ths s expressed by he neracon erm rea- ndcaes wheher he was effcen or no whch s sascally sgnfcan and equal a and. Ths resul shows ha he dfference of he average ozone levels beween he reamen and conrol group has been reduced afer he mplemenaon of he Clean Ar Wors by ppb. More specfcally he esmaed average ozone level n he reamen and conrol group before he Clean Ar Wors mplemenaon was respecvely ppb and ppb resulng o a dfference equal a ppb ( ). Afer he mplemenaon of he he average ozone levels are and n he reamen and conrol group respecvely wh a dfference equal a ppb ( ). Thus based on able 2 he dfference-n-dfference DD esmaor- s he dfference 11

13 beween ppb and ppb ( ppb) whch has been dscussed n he mehodology par. Therefore based on he frs man coeffcen of neres he DD esmaor he Clean Ar Wors s effecve on mprovng ar qualy n he reamen group. The second man coeffcen of neres s he rple DDD esmaor (coeffcen β11) whch s expressed by he neracon erm reawarnng. The coeffcen s negave and sgnfcan and s equal a Ths shows ha he smog alers are more effecve under he regardng ar qualy mprovemen. More specfcally usng equaon (2) he frs erm s he double DID n he reamen group whch s -4.5 ppb and s derved as: The average ozone levels n he reamen group when a smog aler s ssued are ppb (sandard devaon: ) and ppb (sandard devaon: ) n he pos-reamen and pre-reamen perods respecvely resulng o a dfference ppb (59.01 ppb ppb). Smlarly for he non-smog aler days he dfference s ppb (50.11 ppb ppb) and s he second erm of he frs squared brace n relaon (2). The double DID for he reamen group s he dfference beween ppb and ppb (-4.5 ppb). Thus he average ozone levels beween he smog-aler and non-smog aler days have been reduced n he reamen group by 4.5 ppb afer he mplemenaon of he. Smlarly for he conrol group he double DID s he dfference of -3.8 ppb and ppb (-2.62 ppb). Therefore he rple DDD s he dfferences beween he double DD of he reamen and conrol group and s equal a ppb (-4.5 ppb - (-) 2.62 ppb). Fnally he hrd man coeffcen s he DDDD esmaor whch s capured by he coeffcen β14 and s expressed by he neracon erm Trea ProgramWarnngThreshold. The coeffcen s negave and sgnfcan and equal a In ha case he ar qualy has been mproved n he reamen group n comparson o conrol group afer he mplemenaon of he Clean Ar Wors proec and he change of he hreshold and when an ozone warnng s ssued. The DDDD esmaor shows ha he dfferences of he ozone levels beween he wo groups are reduced by ppb when 12

14 smog alers are assocaed wh he mplemenaon of he and he change of he warnng hreshold. Thus he resuls suppor he effecveness of he Clean Ar Wors proec whle he smog alers are addonally mprovng ar qualy when hey are assocaed wh he based n he rple DDD esmaor. Fnally he DDDD esmaor esablshed he effecs of he warnng hreshold change on acual ozone levels. The change of he hreshold addonally mproves he ar qualy n he reamen group relavely o he conrol group. Ths also can be confrmed by he fac ha forecasng and acual ozone levels dffer sgnfcanly. Frsly hs s due o weaher condons. More specfcally he meeorologss use pas weaher condons for he ozone predcons. However as has been dscussed n he leraure revew secon weaher also can nfluence raffc flow and paerns whch raffc volume s no used n her models. Thus by conrollng for weaher condons along wh he Clean Ar Wors s possble o capure hese effecs on raffc volume whch resuls n changes of ozone levels. Secondly by conrollng for me and couny effecs he effecs of he on ozone levels are capured. More specfcally he obecves of hs as s has been dscussed n prevous secon s o encourage ndvduals employees and employers o follow varous pracces n order o reduce he ar polluon especally when a smog aler s ssued. Ths has as a resul o affec he acual ozone levels even f he ozone forecass are dfferen. Regardng he change of he ozone hreshold he acual and forecasng ozone values dffer n boh groups. Ths s because reducng he ozone hreshold addonal warnngs can be ssued. Thus he local governmens n boh groups have o ae measures n order o mprove ar qualy as has been dscussed n secon 3. However he dfference s hgher n he reamen group because of he mplemenaon as he esmaes have shown. (Inser able 3 around here) 13

15 Nex he robusness checs dscussed n he mehodology par are presened. In able 4 he esmaed resuls of regresson (2) usng placebo dummes before he reamen are repored. I becomes clear ha he parallel rend assumpon s acceped because he DD esmaor expressed by he neracon erm rea s sascally nsgnfcan. Ths ndcaes ha n he absence of he Clean Ar Wors he reamen and conrol group would have he same average rend n ozone levels. Ths assumpon holds whenever he placebo dummes change eg. wheher he oo place n 2001 or (Inser able 4 around here) In fgure 2 he DID esmaes for he Clean Ar Wors and regresson (3) ncludng lags and leads of order 1 2 and 3 are presened. More specfcally he blac lne represens he reamen group whou reamen (unreaed) whle he grey lne represens he conrol group. The blac do-lne represens he reamen group afer he mplemenaon of he. The perod s expressed n 3 dfferen me lnes. The frs ndcaes he begnnng of he sample used n hs sudy whch s 2000 whle he second perod ndcaes he perod where he Clean Ar Wors has been esablshed on 1 s March of Fnally perod 3 ndcaes he esablshmen of he change of he ozone warnng hreshold whch oo place on 27 h May of (Inser fgure 2 around here) I becomes obvous ha he rend before he reamen on he average ozone levels s he same beween conrol and reamen groups. Afer he mplemenaon of he Clean Ar Wors he average ozone levels are reduced n a hgher rae n he reaed group han n he conrol group. Therefore based on he robusness checs he common rend assumpon s no volaed ndcang 14

16 ha he devaon n he rend of he observed oucomes (average ozone levels) n he reaed group from he rend of he observed oucomes n he conrol (unreaed) group are drecly arbued o he effec of he reamen as s shown n he fgure Conclusons Ths paper examned he effecs of he Clear Ar Wors mplemenaon on he ozone concenraon levels n Charloe Area n Norh Carolna Sae. Moreover usng a DDDD model he effecs of he smog alers under hs addonally assocaed wh he change of he ozone warnng hreshold from 80 ppb o 75 ppb have been examned. Based on he esmaes he dfference n ozone levels beween he reamen and conrol group has been reduced afer he esablshmen of he Clear Ar Wors and he smog alers have an addonal effec under hs. The resuls are conssen wh he sudy by Cuer and Nedell (2009). More specfcally he fac ha ndvduals respond o STAs suggess ha such volunary nformaon s have a poenal role n regulaory polcy bu such s alone do no appear o be enough for deecng mprovemens n ar qualy; addonal ncenves appear necessary. Thus he mplcaon of hs s ha addonal ncenves are requred besdes he smog ozone days n order o mprove ar qualy such as eleworng carpool vanpool bcyclng publc rans and ohers. There s one maor poenal lmaon of he analyss. The ndvdual behavour on ransporaon mode choce s no examned. Especally n he case of Clean Ar Wors proec where carpool and vanpool s as well as publc rans s encouraged and oher polces are proposed he raffc volume s no explored. As was menoned he purpose of hs sudy s he nvesgaon of he effecveness of he Clean Ar Wors Proec he drec examnaon of ozone forecass and smog alers o acual ozone concenraons and her assocaon wh Clean Ar Wors. 15

17 Addonally oher sudes have already examned he effecs of ozone warnngs on raffc volume and publc healh (Cuer and Nedell 2009; More and Nedell 2011). Acnowledgmens. The auhors would le o han he anonymous revewers for her valuable commens suggesons and consrucve commens ha grealy conrbued o he mprovemen of he qualy of hs paper. Any remanng errors or omssons reman he responsbly of he auhor. 16

18 References Agudelo-Casaneda D. Texera E. Rolm S. Perera F. and Wegand F. (2013). Measuremen of Parcle Number and Relaed Polluan Concenraons n an Urban Area n Souh Brazl Amospherc Envronmen Vol. 70 pp Angrs J.D. and Psche J.S. (2008). Mosly harmless economercs: An emprcs's companon. Prnceon unversy press. Cruzen P.J. (1974). Phoochemcal reacon naed by and nfluencng ozone n unpollued ropospherc ar Tellus Vol. 26 pp Cummngs R.G. and Waler M.B. (2000). Measurng he effecveness of volunary emsson reducon s Appled Economcs Vol. 32 pp Cuer W.B. and Nedell M. (2009). Volunary nformaon s and envronmenal regulaon: Evdence from Spare he Ar Journal of Envronmenal Economcs and Managemen Vol. 58 pp Derwen R.G. Jenn M.E. Saunders S.M. Pllng M.J. Smmonds P.G. Passan N.R. Dollard G.J. Dumrean P. and Ken A. (2003). Phoochemcal ozone formaon n Norh Wes Europe and s conrol Amospherc Envronmen Vol. 37 No. 14 pp Envronmenal Proecon Agency (2008). Ar Qualy Crera for Ozone and Relaed Phoochemcal Oxdans Washngon DC: Envronmenal Proecon Agency. Fgueredo M. Monero A. Lopes M. Ferrera J. and Borrego C. (2013). Ar Qualy Assessmen of Esarrea an Urban Indusralzed Area n a Coasal Regon of Porugal Envronmenal Monorng and Assessmen Vol. 185 pp Granger C. W. J. (1969). Invesgang Causal Relaon by Economerc and Cross-Seconal Mehod. Economerca Vol. 37 pp More E. and Nedell M. (2011). Polluon Healh and Avodance Behavor Evdence from he Pors of Los Angeles Journal of Human Resources Vol. No. 1 pp Pudasanee D. Sapoa B. Shresha M.L. Kaga A. Kondo A. and Inoue Y. (2007). Ground level ozone concenraons and s assocaon wh NOx and meeorologcal parameers n Kahmandu valley Nepal Amospherc Envronmen Vol. 40 pp Roh H.J. Dala S. and Sharma S. (2013). Effec of Snow Temperaure and Ther Ineracon on Hghway Truc Traffc Journal of Transporaon Technologes Vol. 3 pp Schreffler E. (2003). Quanfcaon mehods for denfyng emsson reducons resulng from seasonal and epsodc publc educaon s. Ar Resource Board Fnal Research Repor. Welch E. Gu X. and Kramer L. (2005). The effecs of ozone acon day publc advsores on ran rdershp n Chcago Transporaon Research Par D Transpor and Envronmen Vol. 10 pp

19 Oucome (y g) Conrol group (g = A) Treamen group (g = B) Group dfference (y B - y A) Table 1. Dfferences-n-dfferences mplemenaon Pre-reamen Pos-reamen Tme dfference ( = 1) ( = 2) (y g2 - y g1) y A1 y A2 common rend (y A2 - y A1) y B1 y B2 common rend+ reamen effec (y B2 - y B1) normal dfference (y B1- y A1) normal dfference + reamen effecs (y B2- y A2) reamen effec=(y B2- y B1)- (y A2- y A1) Or (y B2- y A2)- (y B1- y A1) Fgure 1. DID plo example 18

20 Table 2. Summary sascs for daly acual ozone concenraons expressed n ppb No. observaons Mean Sandard Devaon Mn Max Treamen group Perod Ground Level Ozone Treamen group Perod Ground Level Ozone Treamen group Perod Ground Level Ozone Conrol group Perod Ground Level Ozone Conrol group Perod Ground Level Ozone Conrol group Perod Ground Level Ozone Table 3. Quadruple DDDD Esmaes for Equaon (1) Varables (Coeffcens) Esmaed Coeffcens Varables (Coeffcens) Esmaed Coeffcens Trea (β 1) (0.2274) Program Warnng (β 8) (0.3841) Program (1 for 2006 and afer and 0 oherwse (β 2) Warnng (1 for smog aler and 0 oherwse) (β 3) (1.2042) (0.6004) Program Threshold (β 9) (0.2739) WarnngThreshold (β 10) (2.235) Threshold (1 for 2008 and afer and 0 oherwse) (β 4) (0.2808) TreaProgramWarnng (DDD effecveness of smog alers under Clean Ar Wors Regme) (β 11) (0.7553) TreaProgram (DD effecveness of Clean Ar Wors Program) (β 5) (0.3887) Trea ProgramThreshold (β 12) (0.3002) TreaWarnng (β 6) (0.4155) Program WarnngThreshold (β 13) (0.5153) TreaThreshold (β 7) (0.3745) Trea ProgramWarnngThreshold (DDDD esablshmen of he hreshold change effec) (β 14) (0.1131) No. obs R a. Sandard errors are repored beween braces clusered sandard errors a ozone monorng se b. and denoe sgnfcance a he 1% 5% and 10% level c. The conrol varables are: day of he wee monh year ozone monorng ses counes ozone forecasng regonsareas average emperaure wnd speed wnd drecon and solar radaon. 19

21 Table 4. Placebo Robusness chec for DID regresson (3) Varable (Coeffcen) Esmaed coeffcen Summary Sascs TreaProgram (DD effecveness of Clean Ar Wors Program) (β 3) (0.6512) R Square No. of observaons a. Sandard errors are repored beween braces clusered sandard errors a ozone monorng se b. The dependen varable s he acual ozone levels and he conrol varables are: day of he wee monh year ozone monorng ses counes ozone forecasng regons-areas average emperaure wnd speed wnd drecon and solar radaon. Fgure 2. DID Esmaes for he Clean Ar Wors Program usng Leads and Lags 20