Transactions on the Built Environment vol 33, 1998 WIT Press, ISSN

Transcription

1 Transacions on he Buil Environmen vol 33, 1998 WIT Press, ISSN A mehodology and a proposal for reail rip aracion model P. Fadda, G. Fancello Diparimeno Ingegneria Terriorio sez. Traspori, CRIMM Cenra Ricerche Modelli di Mobilia, Universia degli Sudi di Cagliari, piazza d'armi, Cagliari, Ialy Absrac One of he emerging issues in own planning is ha of he effecs of he localisaion of business and services aciviies on mobiliy. In Ialy in paricular he ransformaion of secors such as he food disribuion chain and he lack of care in planning he localisaion of new aciviies are causing unconrolled changes wih devasaing effecs on he urban sysem. The auhors propose a rip generaion model for corner shops and supermarke: he model is disaggeraae for frequency of rip and calibraed for Ialian realiy, where consumers' behaviours are quie differen compared o English experiences. 1 Inroducion One of he emerging issues in own planning is ha of he effecs of he localisaion of business and service aciviies on mobiliy. In Ialy in paricular he ransformaion of secors such as he food disribuion chain and he lack of care in planning he localisaion of new aciviies according o efficiency crieria relaed o he problems of induced raffic, are causing unconrolled changes wih devasaing effecs on he urban sysem. This can be explained by he fac ha mobiliy induced by reail aracors is 17% of he oal urban mobiliy, which is a significan share of nonsysemaic rips. Moreover, he shif owards large disribuion and hard discoun has affeced he habis of he users and consequenly heir disposiion o rips, which have aken on differen connoaions wih respec o he pas. Moreover here is a endency o place reail aciviies

2 Transacions on he Buil Environmen vol 33, 1998 WIT Press, ISSN Urban Transpor and he Environmen for he 21s Cenury away from urban cenres, in more peripheral areas, in he ineres of large reail poles ha creae imbalances in he mobiliy sysem. In some counries single aracor mobiliy models have been se up according o heir characerisics, bu when applied o differen realiies, he models did no provide significaive resuls because of he differen behavioural characerisics of he users(e.g. Bromley^, Cairns'*). Therefore he presen research is no only aimed a defining he coefficiens of he algorihms, bu a redefining heir srucures compleely, saring from he very deerminaion of he significaive variables describing he behaviour of he users (e.g. Barnard^). The research underaken a he Cagliari Universiy CRIMM is focused on small and mediumsized reail aracors, since greaer differences in rip behaviour han wih he large hypermarkes have been observed in Ialy as compared o oher counries. I has in fac been observed ha, as regards he larger aracors, models se up for oher counries can also be used wih discreion in Ialy. To his purpose a programme o define he TIA (Traffic Impac Analysis) of hypermarkes is being se up. This work presens he final resuls in he model definiion phase, which were parly announced a he IVh S.I.D.T. Scienific Seminar in These resuls complee he phase relaing o he opimisaion represenaion models of mobiliy araced by small and mediumsized business generaors. The algorihms provide a very good represenaion level. New sudies are a presen under way a he same reail aracors, in order o analyse change in user behaviour, hus he validiy of he model iself, in an urban secor recenly undergoing srucural changes due o he inroducion of a hypermarke in is disribuion nework (e.g. Fadda ***). 2 Mehodology The mehod provides for an exended invesigaion of he users a he various aracors, as a resul of he observed differences beween Ialy and oher counries (UK, USA and France) in user rip behaviour, funcional organisaion of he reail secor, and ype of ransporaion supplied, wih paricular reference o public ranspor (e.g. Recker ). Daa relaing o rip behaviour, rip aiudes, user percepion of he ransporaion supply sysem, preferences, choice alernaives, ec., have been colleced. Seven shops in he Cagliari area, represening 1000 users, have been analysed. Some of he shops were in an area where a large hypermarke was planned o open a he ime. The daa were processed wih he muliple correspondence and cluser echniques. As already shown in previous papers, he subdivision of users ino clusers wih respec o frequency of use of he shops proved o be he

3 Transacions on he Buil Environmen vol 33, 1998 WIT Press, ISSN Urban Transpor and he Environmen for he 21s Cenury 171 beer echnique in simulaing he differen rip choices of he users. Furhermore, in order o check he weigh variaion of he variables on varying he analysed realiy, an analogous invesigaion was carried ou on 12 shops in hree differen areas in England, o a oal of 800 inerviews; his was jusified by he fac ha rip behaviour is very differen in he wo counries. In he analyic phases of he phenomenon, a significaive pariion of he sudied populaion was possible defined, and for each cluser i was possible o define he represenaive variables of choice of mobiliy. Subsequenly, from he coningency able and by calculaing he of he %, we checked variable independence and possible correlaions in he descripion of he phenomenon. For each cluser, a se made up of 4 or 5 variables was deermined, and he model was calibraed on he variables. Consisenly wih choices made in similar cases, he srucure of model was oriened owards deerminisic funcions (Koppelman ). 3 Analysis and resuls The resuls of his paragraph refer only o daily, morehanonceweekly and nonhabiual frequency users. As already observed, he weekly frequency user caegory gave good resuls in he previous sudy (Fadda^). The parameers were he same as in he previous ess: R and R ha measure he disance beween simulaed and found daa, " saisics^ and prob() ha assess he degree of significaiviy of each coefficien in he model, "F Fisher saisics" and prob(f), ha locae a possible casual disribuion of daa and finally "DurbinWason es" ha deecs auocorrelaion phenomena. The algorihm used wih he daily frequency user caegory is differen in srucure from he one used in he earlier sudy. Raher han a linear ype of funcion, we used a relaion of he mulivariae ype in his case, wih he variables exponenially relaed o he coefficiens and he single erms linked o each oher in a muliplicaive relaion. The following are he main schemes adoped and he resuls obained: scheme n l) y = (xra)*(x2^b)*(x3x:)*(x4''d)*(x^e)*f scheme n 2) y = (x, "A)*(x2/\B)*(x3X:)*(x4''D)*(xrE) y = no. of daily frequency cliens x^ = ne av. shop area (in sq m) scheme n 3) y = (x,^a)*(x2^b)*f x = no. fam. (h.) in he neighbor. scheme n 4) y= (xra)*(x^b)*(x3^c)*f x^ = shop qualiy coefficien scheme n 5) y = (x, ^A)*(x2^B)*(x^D)*F x^ = produc qualiy coefficien scheme n 6) y = (x,/vl)*(x2^b)*(x3^c)*(x^d)* F x no. of parking sies in a 150 m scheme n 7) y= (xra)*(x2^b)*(x3/"c)*(x^e)*f scheme n 8) y= (xra)*(x2/"b)*(x^d)*(x^e)*f scheme n 9) y= (

4 Transacions on he Buil Environmen vol 33, 1998 WIT Press, ISSN Urban Transpor and he Environmen for he 21s Cenury A R r n F F R* R\^ TVW F PrnhfF) The resuls obained wih he funcion scheme are more significaive han in he previous sudy. This shows ha a mulivariae logarihm guaranees a higher simulaion poenial; a "hybrid" scheme beween he linear and he mulivariae ype could also be used in scheme 9), bu he resuls obained showed is oal inefficiency; from he analysis of he daa, he four above menioned variables proved he mos significaive in describing he model; he resuls show ha each of hese variables "explains" a par of he simulaed phenomenon. As, a maer of fac he algorihm schemes wih he highes R and R age s are hose ha include all he variables in he daa analysis. Moreover he individual variables change heir significaiviy on changing he scheme, as can be seen from a reading of he " saisics" and prob() s. This shows ha in fac all variables have a high simulaion poenial. The only schemes where i was no

5 Transacions on he Buil Environmen vol 33, 1998 WIT Press, ISSN Urban Transpor and he Environmen for he 21s Cenury 173 possible o calculae hese s because he funcion convergence was no obained, were 1) and 8); # "Fisher F saisics" and prob(f) s show ha for schemes 2 and 5 funcion convergence is no due o a casual arrangemen of he analysed erms, bu o a real inerpolaion of he obained funcion; * Since in he 9 schemes DurbinWason es s are clearly higher han uniy, here are no auocorrelaion phenomena. From a comparison of he resuls, i can be seen ha he he observed daa is bes inerpolaed wih he model relaing o scheme 2), for which excellen resuls have been found on all he saisically significan parameers. The obained funcion is: ha gives he following expression when ransformed ino logarihmics: log(y)= [1.47*log (x,)] + [0.83Mog(x2)j + [1.86*log(x,)] + [3.77*log(x,)] *!og(xs)] where he log of he number of araced users appears in he firs member. I is ineresing o noe ha in he inernaional lieraure he logarihmic form is he mos commonly used for mobiliy simulaion models araced by commercial ype generaors. In agreemen wih wha has previously been poined ou, oo in his case he coefficien of he "ne available shop area (in sq m)" is of a negaive sign. In fac, his caegory refers o he daily ype of users, who prevalenly visi small shops (corner shops, small supermarkes). Moreover, he negaive sign referring o he variable "no. of parking sies in a 150 m radius" is jusified in he same way, since he users are prevalenly pedesrians. To check he represenaion power of he chosen funcion, seven shops have been chosen from he sample, and heir observed daily mobiliy was compared wih he calculaed by he model. The obained resuls are summed up in he ab. 1 (page 9). I can be seen ha on he whole he model performs very well, wih an expeced error of abou 12%. I can be saed herefore ha for he caegory under sudy, his model is o be considered final. As regards he morehanonce a week user caegory, even in his case a mulivariae ype of funcion was used insead of a linear ype of funcion ha has no given good resuls previously. The main adoped schemes and he resuls obained are repored below: scheme n l) y = (x,^a)*(x2^b)*(x3x:)*(x4^d)*(x5^e)*f scheme n 2) y = (x^a)*(x2^b)*(x3^)*(x4^d)*(x5^e) y = no. of more week freq.cliens x^ ne av. shop area (in sq m) scheme n 3) y = (x,"a)*(x2^b)*f x^ no. fam. (h.) in he neighbor.

6 Transacions on he Buil Environmen vol 33, 1998 WIT Press, ISSN Urban Transpor and he Environmen for he 21s Cenury scheme n 4) y= (x,*a)*(x2*b) scheme n 5) y= (x^a)*(x2^b)*(x3x:) scheme n 6) y= (x,"a)*(x2"b)*(x3*c)*(x4"d) scheme n 7) y = (xi^)*(x2*b)^x3^)*(x4*d)* scheme n 8) y= (x^a)*(x2"b)+(x3^)*(x4'"d)* scheme n 9) y= (x^a)+(x2^ x^ = no. of analog.shops in a 500 m x^ = shop qualiy coefficien x = produc qualiy coefficien A R r r> F F R* R\w HAV F Prnh(F) even in his case he mulivariae ype of srucure clearly gives he mos rueolife resuls. In he case of schemes 1) and 9) he "saisics " and prob() s do no appear since funcion convergence was no reached; significaiviy of all variables obained by daa analysis is confirmed by he excellen resuls obained for schemes where he variables are always presen and consequenly by he poor resuls obained by he schemes where he number of variables is less han four; schemes 2) and 7) are where excellen resuls were obained, wih pracically similar s: all saisical parameers used in he search

7 Transacions on he Buil Environmen vol 33, 1998 WIT Press, ISSN Urban Transpor and he Environmen for he 21s Cenury 175 for he bes algorihm have clearly confirmed he goodness of he wo chosen models; for boh he hypoheses of casual daa arrangemens and auocorrelaion phenomena can be ruled ou; in boh scheme 2) and scheme 7) he coefficien of he variable "ne available shopping area (in sq m)" is negaive since, also because of he similariy of he represenaive variables used, he behaviour of he morehanonce weekly users is very similar o ha of he daily users; from " saisics" and prob() s, he high significaiviy of all he variables in he descripion of he phenomena emerges; i is o be poined ou ha in scheme 7) he s relaing o he consan reveal ha i is subsanially useless, hus making he wo models equal. Therefore he chosen algorihm is no.2: he deermined funcion is: y [x.*(!9.1)]*[x2*(23.4)]*[x j*(88.9)j* 1x^(46.4)]*[xs*(32.6)] Transformed ino logarihmics: logcv)= [19.1 *Iog (x,)] + [23.4*log(x2)] *log(xj)l + [46.4*log(x<)J + [32.6*log(xs)J where he log of he number of araced users appears in he firs member. The mos represenaive funcional form for he morehanonce a week caegory of users is analogous o ha obained for he daily users. This furher confirms he similariy in behaviour beween he wo groups. In order o check he represenaive capaciy of he funcion, he obained morehanonce a week was compared wih he referring o he sample shops esimaed by he model. The resuls are in ab. 1 (page 9). The high sensiiviy of he model ( in all cases) presupposes a casual phenomenon of coincidence beween calculaed and found s. Though his coincidence is o be considered an excepional even, i confirms he absolue efficiency of he funcion. As regards he nonhabiual frequency user caegory, a similar procedure o he one used in he wo previous cases was adoped. The main adoped schemes and he resuls obained are repored below: scheme n l) y= (A*Xi)+(B*X2)+(C*X3)+(D*X4>+E scheme n 2) y= (A*Xi)+(B*X2)+(C*X3)+(D*x4) y no. of occasional frequency cliens x = aver, disance shops and neares parking scheme n 3) y = (x,^a)*(x2^b)*(x3^c)*(x4^d)*e x = no. of parking sies in a 150 m radius scheme n 4) y = (x,*a)*(x2"b)*(x3"c)*(x4"d) x^ no. of opening hours oher han scheme n 5) y = (X *A)*(X2*B)*(X4*D)*E and x = aver. dis. from he disric, road nework scheme n 6) y= (x,*a)*(x2*b)*(x3*c)*e scheme n 7) y = (x,"a)*(x2^b)*(x3/\c)*(x4^d)+e scheme n 8) y= (xi*a)*(x2*b)+e scheme n 9) y= (

8 Transacions on he Buil Environmen vol 33, 1998 WIT Press, ISSN Urban Transpor and he Environmen for he 21s Cenury l A B C D E R* R\gg DAY F I can be seen immediaely ha he s of he associaed saisical parameers in all he schemes are on average lower ha hose found for all he proposed models. I is also seen ha i is more difficul o model a caegory of users wih a behaviour ha is no easily classified, a caegory moved by a casualiy ha is characerised by many uncerain variables ha are no easily deermined. Repeiiveness of acion (in his case he rip) characerising nonhabiualiy as such, he kind of repeiiveness, ha is, ha would allow a beer represenaion, is in fac missing in he ype of behaviour associaed wih he users. Moreover, owing o he peculiariy of he rip iself, he variables ha come ino play are clearly more numerous han hose referring o anoher ype of rip. For his reason he obained resuls can be considered good, in spie of a lower performance han wih previous models; in his case also he validiy of he linear funcion, he funcion ha is ha has given good resuls also for he weekly frequency caegory of

9 Transacions on he Buil Environmen vol 33, 1998 WIT Press, ISSN Urban Transpor and he Environmen for he 21s Cenury 177 users, has been esed. However, we have preferred o use a mulivariae funcion, ha should be analogous o he previous wo cases; he schemes where he resuls have been more saisfacory are no. 3 and no. 7, ha is hose ha conain all he variables shown in he analysis of he previous daa; from he " saisics" and prob() s i emerges ha he mos significaive variable is he "no. of parking sies in a 150 m radius"; his is due o he fac ha he nonhabiual users are mainly passing users, ha prevalenly use privae cars, and herefore he presence of a parking sie in he neighbourhood becomes a key elemen in choosing he shop. From a comparison of he mos significan daa i can be seen ha scheme no. 7) is he one ha presens he bes resuls; he deermined funcion is he following: y = [X,^(0.42)]*[X2^(1.25)]*[X3^(0.14)]*(X4^(0.58)]H(36.01) Since his funcion conains a sum operaor, i canno be ransformed ino a linear funcion by going hrough a log funcion. In he able below here are he resuls of performance level of algorihms: Shopn.l Shop n.2 Shop n.3 Shop n.4 Shop n.5 Shop n.6 Shop n. 7 Average found DAILY USERS model Sensiivi y 90% 99% 74% 99% 82% 78% 97% 88% MORETHANONCE A WEEK USER found model sensiiviy % % found NON HABITUAL USER model ab. 1: Comparison beween found and model resul Sensiiviy 99% 96% 71% 96% 77% 64% 86% In spie of he difficulies in codifying he behaviour of nonhabiual users hrough a model, he average sensiiviy (86%) is very good. I is imporan, however, o poin ou ha, he resuls obained for he daily and morehanonce a week frequency users are eiher equal or vary wihin a very resriced inerval. In his case, however, since he model's sensiiviy flucuaes beween a minimum of 64% and a maximum of, predicion is more uncerain. I is imporan o poin ou, however, ha

10 Transacions on he Buil Environmen vol 33, 1998 WIT Press, ISSN Urban Transpor and he Environmen for he 21s Cenury aking ino accoun he complexiy of he phenomenon represened and of he known difficuly in schemaising he behaviour of nonhabiual users, he resuls obained during calibraion are good enough o consider his model final for his caegory. 4 Conclusion The sudy has reached he objecive of defining he represenaive algorihms capable of reliably simulaing for each caegory of user he mobiliy araced by small and mediumsized shops. In some cases (morehanonce a week frequency users) he resuls have been very good, wih negligible error percenages, while in ohers (nonhabiual users) he research has been harder and gave less significaive resuls, bu sill i has been reliable in predicion of he mobiliy. In he presen phase, he objecive is o incease he daa bank in order o exend he reference base for he calibraion of funcion coefficiens on a greaer number of generaors in differen pars of he counry. This exension is inended mainly for comparison wih he regional daa relaing o Sardinia, he only realiy so far aken up as a reference in defining he model. 5 References Barnard, P. O., Modelling shopping desinaion choice: a heoreical and empirical invesigaion, Ausralian Road Research Board, SR 36, Vicoria, Bromley R., Thomas C., Reail change: conemporary issues, UCL Press, London, Cairns, S., Travel for food shopping: he Fourh Soluion, Traffic Engineering and Conrol, 36 (7) pp , 1995 Fadda P., Fancello G., Choice facor analysis in food shopping ravel behaviour, Proc. 2nd Urban Transpor & he Environmen eds. J.M. Baldasano, L.J. Sucharov, Compu. Mechanics Publ., Souhampon &Boson, pp , Fadda P, Fancello G (1995) 'La mobilia araa da generaori di ipo commerciale: la defmizione di una meodologia per il caso ialiano 'Proc. of Seminario S.I.D.T., Franco Angeli, Milano pp.4564, 1997 Fadda P, Fancello G (1995) 'Disaggregaion level and variables choice in reail rips: comparison beween Ialy and England, behaviour' Proc. 1s Urban Transpor & he Environmen eds. L.J. Sucharov, Compu. Mechanics Publ., Souhampon &Boson, pp , 1995 Koppelman, F S (1980) 'Consumer Analysis of ravel choice Behavior' Journal ofadvanced Transporaion, 10 (4), Recker W, Kosyniuk L, (1978) 'Facors influencing desinaion choice for he urban grocery shopping rip', Transporaion, 1 (3), 1933