Assessing Willingness to Pay to Use an Underground Car Park

Transcription

1 Assessng Wllngness to Pay to Use an Underground Car Park Ths Feature dscusses modelng user parkng behavor to determne wllngness to pay (WTP) n exchange for qucker access to the fnal destnaton. The calculaton of WTP s fundamental n the evaluaton of any socal and economc project. WTP s calculated from a stated preferences survey and from the estmaton of multnomal logt models. By LUIGI DELL OLIO, Ph.D., ANGEL IBEAS, Ph.D. AND JOSE LUIS MOURA, Ph.D. INTRODUCTION Parkng polces are an mportant part of urban plannng and have extensve repercussons on the management of travel demand polces. Installng pad parkng areas, even n small towns, s often an unpopular measure that most ctzens do not understand. The realty s that street space s a scarce publc commodty; therefore ts use should be pad for ndvdually, smlar to any other publc property. Ths stuaton s extremely crtcal n cty centers and other areas wth hgh populaton denstes and commercal actvty. In Europe, parkng spaces are generally regulated n two ways: through blue zones (regulaton of space and watng tme) and publc parkng (regulaton by tarff). Publc parkng can be suppled usng ether surface or underground parkng spaces. Wllngness to pay (WTP) s a fundamental varable that should be used n the socal and economc evaluaton of constructon projects and car park management because t provdes a clear dea of the tarff cost dependng on other factors that are mportant to the user. Normally, underground car park constructon s assocated wth urban development. Determnng the szes of these parkng areas, calculatng the demand and fxng the method of payment and the payment amount are not smple tasks. Constructon costs are mportant when evaluatng the economc mpact of these projects. Once the work s fnshed, the tarffs charged represent the man source of ncome. Therefore, t s mportant to study user behavor when faced wth dfferent prcng strateges n order to fx the correct tarff. Relevant studes can be found n nternatonal lterature. One such study models parkng choce through a stated preferences survey. 1 Another focuses on parkng demand n Sydney, Australa. 2 In another study, dfferent types of parkng were chosen and a logt model was run to model parkng choce as a functon of correspondng attrbutes. 3 These artcles also provde many examples of studes done on the nfluence of parkng fees and even nclude parkng smulaton models lke PA- MELA. 4 7 User responses to changes made n the supply, locaton, tarff and accessblty of parkng places have also been recorded. 8 PROBLEM AND METHODOLOGY Ths feature dscusses the constructon of an underground car park n Santoña, Cantabra, Span. Santoña s a coastal and tourst town wth less than 3,000 resdents; the populaton ncreases durng the summer due to toursm. It also has an mportant fshng fleet. The regonal government of Cantabra proposed buldng a lesure area n Santoña close to the fshng port. Ths area would nclude restaurants, bars and shops and would be complemented by the creaton of large pedestran-only areas. Thus, the problem of parkng spaces to serve ths area emerged. The regonal government ordered a study on the constructon and management of an underground car park close to the lesure areas. Ths techncal, economc and socal vablty study also called for the reorganzaton of surface parkng, along wth the management of the future underground car park. Three requrements needed to be resolved to carry out ths vablty study: 1. Defne the supply of parkng spaces needed to satsfy the demand of users of the lesure area, accountng for spaces that would be elmnated on the surface by pedestran-only areas. 2. Consder three choce possbltes for the user: street parkng (SP); pad street parkng, defned as ordenanza lmtadora de aparcamento (OLA), or order for restrcted parkng; or future underground car park (UP). ITE Journal on the web / March

2 Table 1. Expermental desgn: varables consdered n stated preferences survey. Varable 1st level 2nd level Random varaton Tarff for underground parkng (TUP) 0.8 _/hour 1.5 _/hour Tarff OLA (TOLA) 0.6 _/hour 0.8 _/hour Access tme to underground parkng (ATUP) Access tme to OLA (ATOLA) Access tme to street (ATS) Tme to destnaton from underground car park (DTUP) Tme to destnaton from OLA (DTOLA) Tme to destnaton from street (DTS) Determne the dstrbuton of users among the three avalable parkng optons. 3. Determne WTP per hour of parkng n the UP to reduce access tme to the fnal destnaton from the car park. 5±3*ξ 1 10±2*ξ 3 Note that street parkng s currently free of charge n the study area. Also, tarffs for underground parkng are hgher than those for surface parkng. Underground car parks are supervsed and offer sgnfcantly hgher levels of securty both n terms of robberes and mnor collsons. They also offer easer payment and more comfort than surface car parks. A stated preferences survey was desgned to determne the potental demand of car travelers vstng the new lesure area n Santoña. A study was conducted focusng on the varables that affected each user s choce of parkng. The data obtaned n the survey were used to estmate a seres of multnomal logt models n order to defne the dstrbuton of users among the three types of avalable parkng. The fnal results of the models showed the users WTP n order to save tme n reachng ther fnal destnaton. Ths feature presents a new methodology that allows a trustworthy WTP to be calculated wth a small degree of varablty. It also allows a tarff to be fxed that agrees wth the users WTP to reduce access tme to ther fnal destnaton. STATED PREFERENCES: EXPERIMENTAL DESIGN The Gude to Forecastng Travel Demand wth Drect Utlty Assessment was used for the expermental desgn of ths project, whch conssted of proposng a seres of hypothetcal stuatons defned by a seres of varables assumed to be hghly nfluental on the parkng choce made. 9 In ths case, fve varables were consdered, and each varable had two levels (see Table 1). Ths gude also contans a seres of tables that allow these varables to be combned wth ther respectve levels under certan stuatons (see Table 2). In a prevous study, problems n calculatng dscrete choce models were found. Excessve value was gven to WTP, whch was not representatve of the real stuaton. Ths was caused by varablty n the answers of the ntervewees when the stuatons were changed. 10 Ths problem may be approached by provdng the ntervewees wth stuatons gven random value varables, thereby coverng the fullest range of possble stuatons. The prncple varables access tme to underground parkng (ATUP), access tme to parkng n OLA (ATOLA) and destnaton from underground parkng (DTUP) were calculated from an average value prefxed by +/-; a determned value generated by a random number between 0 and 1 (ξ 1, ξ 2, ξ 3 ). Therefore, ATUP, ATOLA and DTUP show greater varablty, and ther nfluence on user choce can be studed n greater detal, provdng more trustworthy WTP values. ATUP s defned as the tme from the moment the user enters the car park to fndng a place and parkng. ATOLA, or access tme to street (ATS), s defned as the tme from the moment the user s vehcle enters the area where surface parkng s avalable to fndng a place and parkng. The values gven to ATUP and ATOLA are dfferent because t was observed that fndng a parkng space n an underground car park s easer due to ts hgher cost compared to surface parkng. Table 2. Expermental desgn: stuatons consdered by users n choosng type of parkng. Tarff underground parkng Tarff OLA Access tme to underground parkng Access tme to OLA Access tme to street Tme to destnaton from underground car park Tme to destnaton from OLA Tme to destnaton from street Stuaton TUP [_/hour] TOLA [_/hour] ATUP ATOLA ATS DTUP DTOLA DTS ±3*ξ ±3*ξ ±3*ξ ±3*ξ ±3*ξ ±3*ξ ±3*ξ ±3*ξ ITE Journal on the web / March 2009

3 Table 3. Dscrete choce models and WTP. Varable Parameter Mod. 1 Mod. 2 Mod. 3 Mod. 4 Mod. 5 Mod. 6 Mod. 7 CP BP Parkng-specfc constant CO BO OLA-specfc constant F [_/hour] FA Tarff TA TI Accessblty to fnal destnaton INC [_/month] IN Income AGE AG Age SEX SE Sex F_D FD Daly frequency of journey F/INC FAD Tarff/Income Log lkelhood functon l(θ) Log lkelhood, no coef. l(0) Log lkelhood, const. only l(c) WTP [$/hour] WTP [ /hour] * 1 = U.S. $ (as of 08/10/07) Fgure 1. Graphc cards smplfed the answer process by llustratng the dfferent attrbutes that nfluenced the choce of parkng type. The value of ths varable may appear hgh, but the lmted supply of surface spaces and user reluctance to park underground for fear of delays caused by congeston must be consdered. Smlarly, tme to destnaton under any of the possbltes s defned as the tme taken by the user to travel from the moment of parkng to reachng the fnal destnaton. From exstng studes on parkng n smlar areas, t was noted that ATUP was n the range of 2 to 8. Therefore, ths varable was gven a varablty of 5±3*ξ 1. Smlarly, for ATOLA, a value of was taken. In the same way, access tme to fnal DTUP was 10±2*ξ 3, based on the dstance between the future locaton of the underground car park and the lesure area. Other varables requested n the survey were sex, age, ncome and frequency of journey (see Table 3). All of ths nformaton was compled and ncluded n the stuatons shown n Table 2. Graphc cards were desgned to mprove user understandng of the stuatons beng sampled. These cards smplfed the answer process by graphcally llustratng the dfferent attrbutes that nfluenced the choce of parkng type (see Fgure 1). WTP values can be calculated from the data obtaned n the survey. The fact that a user s more or less wllng to pay n order to save tme s calculated from ther normal behavor. The correct tarff to charge can be establshed from ths nformaton. ESTIMATION OF MODELS AND WTP To calculate WTP to reduce access tme to the fnal destnaton, an accessblty varable was consdered for each choce. WTP was calculated to ncrease accessblty to the fnal destnaton, assumng that the user values the overall tme taken n parkng plus the tme to reach hs or her fnal destnaton. 11 A choce context had to be defned, whch conssts of the dfferent choce optons open to the user and the consequences of each n terms of tme savngs and cost. WTP for reducng access tme to fnal destnaton was calculated by estmatng varous dscrete choce models n a step fashon, fnally yeldng the models ITE Journal on the web / March

4 n Table 3. The method normally used to estmate these models was maxmum lkelhood. These models show how all of the parameters have the correct sgn. All of the varables used are sgnfcant at a confdence level of 95 percent, except the sex varable (90 percent). The frst fve models were ranked by usng the lkelhood rato test gven that sad models are comparable two by two, as one s a restrcted verson of the other. Based on ths analyss, Model (Mod.) 5 > Mod. 3 > Mod. 4 > Mod. 2 > Mod. 1. The same analyss was completed for Mods. 6 and 7, whch ntroduced the tarff varable dvded by ncome. From ths analyss, Mod. 7 > Mod. 6 was determned. WTP was calculated usng the formula: dc WTP = dt Table 4. Dscrete choce models and WTP of a smlar study. Varable Model 1 Model 2 CP Parkng-specfc constant DA [klometers] Accessblty to fnal destnaton F [ /hour] Tarff [DA] [Accessblty to fnal destnaton] Log lkelhood functon l(θ) Log lkelhood, no coef. l(0) Log lkelhood, const. only l(c) WTP [$/hour] WTP [ /hour] * 1 = U.S $ (as of 08/10/07) Source: Ibeas, A., L. dell Olo and J.L. Moura. Wllngness to Pay for Access Tme Savng: Some Evdences. Proceedngs of Euro Workng Group on Transportaton, Bar, Italy, V / t = V / c (1) Note that the subjectve value of tme s the margnal rate of substtuton between journey tme and cost. It measures an ndvdual s wllngness to pay for tme savngs and s calculated as the dervatve of the cost of choce (c ) wth respect to tme (t ), wth V beng the utlty assocated wth choce. In the partcular case of Mod. 1, the measure can be wrtten as: Vp / ( TA) WTP = (2) V / ( F ) p where: V p = utlty functon of parkng n the underground car park; TA = accessblty to fnal destnaton n (tme lookng for a space + access tme to fnal destnaton; and F = tarff n _/h of underground car park. The fnal column n Table 3 shows the values obtaned for WTP to reduce access tme to the fnal destnaton. DISCUSSION AND CONCLUSIONS It s nterestng to note how WTP to reduce access tme to the fnal destnaton stays practcally constant and does not change when the model specfcaton s changed. Several studes show that more restrctve models tend to underestmate the value of tme; however, varatons should not be found between dfferent models Ths parallels the present study where the WTP only vares between _/hour n Mod. 1 and _/hour n Mod. 3. A smlar study prevously proposed used a bnary choce context (pad underground parkng and free street parkng) but dd not use random numbers to generate ndependent varables. The study obtaned heterogeneous WTP values that were hgher than the values obtaned n ths study, dependng on the model specfcaton (see Table 4). 16 Ths modelng exercse shows that f the choce context s not well specfed and the varables nfluencng choce are not modeled correctly, dfferng WTP values can be obtaned dependng on the model specfcaton. All of these greatly affect the results of the vablty study for the new car park and thus the fxng of the fnal tarff. 17 As can be seen from the proposed methodology, the value of WTP s calculated from real observatons by performng a stated preferences survey, runnng dscrete choce models and dervng utlty functons wth respect to cost and tme. It s mportant to correctly calculate WTP, because fxng a tarff that s hgher than the WTP value obtaned could cause a sgnfcant reducton n the demand. On the other hand, fxng a tarff that s lower than the WTP value would ncrease the demand, resultng n an ncome that may affect the proftablty of the car park. Fnally, the values obtaned for WTP are very close to the values of the tarffs currently beng charged n underground car parks n the Cantabra area, whch are around 1 _/hour. The average of the values calculated n Table 3 s 0.98 _/hour. Therefore, small reductons n tarff may ncrease the demand enough to be benefcal to both users and companes, wthout affectng proftablty and the tme perod for payng off the ntal nvestment. n References 1. Axhausen, K.W. and J.W. Polak. Choce of Parkng: Stated Preference Approach. Transportaton, Vol. 18, No. 1 (1991): Hensher, D.A. and J. Kng. Parkng Demand and Responsveness to Supply, Prcng and Locaton n the Sydney Central Busness Dstrct. Transportaton Research, Vol. 35 (2001): Van der Goot, D. A Model to Descrbe the Choce of Parkng Places. Transportaton Research, Vol. 16A (1982): Kuppam, A.R., R.M. Pendyala and M.V. Gollakot. Stated Response Analyss of the Effectveness of Parkng Prcng Strateges. Transportaton Research Record, No (1998): Banco, M.J. Effectve Transportaton Demand Management: Combnng Parkng Prcng, Transt Incentves and Transportaton Management n a Commercal Dstrct of Portland, Oregon. Transportaton Research Record, No (2000): ITE Journal on the web / March 2009

5 6. Hess, D.B. Effect of Free Parkng on Commuter Mode Choce Evdence from Travel Dary Data. Transportaton Research Record, No (2001): Van der Waerden, P.H. Tmmermans and A. Borgers. PAMELA Parkng Analyss Model for Predctng Effects n Local Areas. Transportaton Research Record, No (2002): Ferguson, E. Parkng and Accessblty. Access to Destnatons. Oxford, Unted Kngdom: Elsever, Kocur, G., T. Adler, W. Hyman and B. Aunet. Gude to Forecastng Travel Demand wth Drect Utlty Assessment. Report No. UMTA- NH Washngton, DC, USA: U.S. Department of Transportaton, Ibeas, A., L. dell Olo and J.L. Moura. Wllngness to Pay for Access Tme Savng: Some Evdences. Proceedngs of Euro Workng Group on Transportaton, Bar, Italy, Tran, K. Recreaton Demand Models wth Taste Dfferences Over People. Land Economcs, Vol. 74 (1998): Hensher, D.A. The Valuaton of Commuter Travel Tme Savngs for Car Drvers: Evaluatng Alternatve Model Specfcatons. Transportaton, Vol. 28 (2001): Hensher, D.A. Measurement of the Valuaton of Travel Tme Savngs. Journal of Transport Economcs and Polcy, Vol. 35 (2001): Tran 1998, note 11 above. 15. Carlsson, F. The Demand for Intercty Publc Transport: the Case of Busness Passengers. Appled Economcs, Vol. 35 (2003): Ibeas, dell Olo and Moura 2006, note 10 above. 17. Ibd. LUIGI DELL OLIO, Ph.D., s a professor of transportaton system engneerng. He earned hs Ph.D. from the Unversty of Burgos, Span and hs master s degree n engneerng from the Techncal Unversty of Bar, Italy. Hs research focuses on transport plannng and travel behavor. He s a member of the Transportaton System Research Group (GIST). ANGEL IBEAS, Ph.D., s a professor of transport. He earned hs Ph.D. from the Unversty of Cantabra, Span. Hs research focuses on transport plannng, travel behavor and ntellgent transportaton systems. He s the drector of GIST. JOSE LUIS MOURA, Ph.D., s a professor of transportaton system management. He earned hs Ph.D. from the Unversty of Cantabra. Hs research focuses on transport plannng and operatonal research. He s a member of GIST. ITE Journal on the web / March