-CONG NGHE MMM mi
XAC D I N H THCil GIAN HANH TRINH
CUA DONG GIAO THONG HON HOP BANG THIET Bl DO TlM WI-FI
MAI VAN HIEU So mon Duong 86, Khoa Cong Trinh,
Truang Dai hoc Giao thong Van Tdi
Tom tit: Trong diiu kien dong giao thong hdn hap vai xe may chiim ti le lo'n, cac phwang phap thu thap sd lieu truyin thing gap nhiiu khd khan. Nhd qua trinh phat triin nhanh cua cac thiet bi di dong cim tay, thiit bi dd tim Wi-Fi se la cd thi thu thap dwac thong tin hanh trinh cua ngwdi tham gia giao thdng, tir dd cd the tinh toan dwac thai gian di chuyen, mot trong nhirng chi tieu quan trong ciJa mire do phuc vu (LOS). Muc tieu eua nghien ciru la tien hanh thwc nghiem viee sir dyng thiit bi do tim Wi-Fi di xac dinh thdi gian di chuyin trong dieu kien ddng giao thdng hdn hap a Ha Noi, ddng thai nghien eiru kiem tra do chinh xac cua phwang phap Tip khoa: Thdi gian hanh trinh, ddng giao thdng hdn hap, MAC address, Thiit bi dd tim Wi-Fi Abstract: In mixed traffic of developing countries where four-wheeler vehicles are not the dominant in the roads, observation of traffic states is still difficult. By the spreading of smart devices, Wi-Fi scanner possibly detects a part of the human travels. They are expected to be used for observing travel time which Is one of the significant index of Level of Service (LOS).
The objective of this paper is to demonstrate the implementation of the travel time estimation method for mixed traffic by Wi- Fi scanner data, and to verify the method by the experimental observation in Hanoi, the capital of Vietnam.
Keywords: Travel time. Mixed traffic. MAC address, Wi-Fi Detector
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Cung vdi s y phat then ciia kmh te xa hgi, sd luang 6 td tham gia giao thong tang nhanh trong nhu'ng nam gan day Tuy nhien, xe may van la phuang tien di chuyen pho b i i n nhat tai Viet Nam, dac biet la d eac thanh pho ldn nhu Ha Ngi.
Chinh dieu nay tao cho ddng giao thdng hdn hap d Viet Nam nhCrng dac diem neng biet va r i t khd cd the ap dung nh&ng ly thuyit giao thdng dien hinh tren t h i gidi.
Trong ddng giao thdng hdn hap, cae phuang tien ed xu hudng di c h u y i n khong theo lan cd dmh (Kiran va Verma, 2016), vi vay, n h i i u nha nghien eii'u da co g i n g tao ra nhu'ng md binh giao thong phu hgp, vi du nhu Khan va Maim (1999), Powell (2000), Nair(2011), Meng (2007), Nguyen va Hanaoka (2011), hay Shiomi (2012), Nhung viec irng dung cac md hinh nay vao d i i u kien ddng xe b i n hgp thuc t i gap nhieu khd khan, khdng ehi bdi vi tinh phirc tap eua md hinh, ma con do viee thu thap sd lieu giao thdng d i u vao edn r i t ban e h i . Luu tuang xe, van t i c ddng xe va tl le giCra d td va cac loai phuang tien khac la ba trong sd nhung dai lugng can thiet de cd the danh gia mgt ddng giao thong hdn hgp Thdi gian hanh trinh eung la mdt dai lugng rat quan trong cho viet xac dinh mii'c do phuc vu ciia tuyen d u d n g , Tuy nhien, nhirng phuang phap thu thap s i lieu giao thdng truyin t h i n g lai thudng khdng the eung d p d i y du nhirng dai lugng tren, Mgt vai nghien ciru cua Li (2011) hay Mallikarjuna (2009) da dua ra giai phap su' dyng phuang phap nhan dien hinh anh de d i m xe t u dgng, Phuang phap nay ed the thu thap d u g c ca luu lugng xe, quy dao chuyen ddng cua xe.
cung nhu ty le thanh p h i n ddng xe. Nhung tinh chinh xac cua nhan dien hinh anh giam dang ke trong khoang thai gian gid cao diem.
G i n day, t h i i t bi dd tim Wi-Fi da d u a c dua vao mdt vai nghien ciru nhu la mgt cdng eu thu thap dCr lieu giao thdng. Bat cir khi nao eac thiet bj dl dgng thong minh nhu dien thoai di ddng hay may tinh bang bat chir'c nang Wi-Fi, nd cung se phat ra mpt tin hieu d i do tim vao diem ket ndi Wi-Fi xung quanh T h i i t bi dd tim Wi-Fi se thu thap tin hieu do va ed the nhan dang cae t h i i t bi thong minh qua MAC address (Media Access Control) ciia t h i i t bj. Thai diem khi mdt ngudi e l m dien thoai di qua mdt t h i i t bi dd tim Wi-Fi se duac ghi lai, va khi ngudi nay di qua hai vi tri t h i i t bl, thai gian di chuyen giOa hai d i i m cd the dugc xae dmh Musa (2011) nghien cicu sir dyng thiet b| dd tim Wi-Fi trong d i i u kien ddng giao thdng truyin thong a My. Nghien cu'u chi ra r i n g k i t qua thdi gian di chuyen tinh toan duae cd sai s i nhd han lOs. Tuy nhien, do so luang d i u phuang tien cua ddng giao thdng truyin t h i n g la khdng nhieu, vi vay viee sir dung thiit bl dd tim Wi-Fi la khdng hieu qua, neu so sanh vdi cac phuang phap thu thap du' lieu giao thdng truyin thdng khac nhu GPS. Abedi (2015) da t i i n hanh thir nghiem de nghien eiru tinh ehinh xac khi sCr dung t h i i t bi dd tim Wi-Fi trong xac djnh thdi gian di chuyen ciia ngudi di bd, ngudi chay bd va ngudi 6i xe dap tai LJc Ket qua r i t kha quan vdi viee khdng chi xae dinh chinh xac thdi gian di chuyen gii>a hai VI tri eiia ba nhdm ngudi ma con cd t h i phan loai dya vao t i c dg di c h u y i n ciia tirng nguai. ^ ^ Nhu'ng nam g i n day, viec si> dgng dien thoai thdng minh, dgc K"
^
f MMM KHOA HOC - CONG NGHE
nhirng thanh pho Ign a Viet Nam nhu Ha Ndi la rat p h i bien. Ngoai ra, thdi quen eiia ngudi s u dung dien thoai thudng giQ' che dg Wi- Fi 24/24, ke ca khi dang di c h u y i n tren d u d n g Chinh vi vay, day la mdt ngudn du' lieu giao thdng t u a n g doi ldn de khai thac. Tuy nhien, trong dieu kien giao thdng thuc t i d Ha Ndi, dac biet vao gid cao diem, khi cac xe di chuyen hdn loan, r i t khd de cd the phan biet dupe van t i c di c h u y i n cua cac loai phuang tien tham gia giao thong khae nhau. Ngoai ra, viec s u dyng t h i i t bi dd tim Wi-Fi yeu eau kinh phf dau t u va van hanh khdng qua ldn, phu hop vdi nhCrng qude gia dang phat trien d khu vuc ehau A nhu Viet Nam, Do dd, myc tieu ciia nghien cii'u nay la thir nghiem viec SU' dung t h i i t bj dd tim Wi-Fi d i thu thap du' lieu giao thdng va xac dmh thai gian di chuyen trong d i i u kien ddng hon hgp, Dk thuc hien myc tieu nay, nghien oju t i i n hanh thuc nghiem tren mdt true d u d n g d Ha Ndi de k i i m tra dp chinh xac khi xac dmh thdi gian di chuyen bang t h i i t bi do tim Wi-Fi,
Phan edn lai ciia nghien ciru se d u a c trinh bay nhu sau: phan 2 trinh bay phuang phap nghien ciru s u dung t h i i t bi dd tim Wi-Fi de xac dinh thai gian di c h u y i n ; p h i n 3 md ta thu'C nghiem; t i i p theo, phan 4 trinh bay phan tich so lieu tCf thuc nghiem; c u i i cung phan 5 d u a ra k i t luan va k i i n nghj
2. PHlTdHG PHAP NGHIEN CUU 2.1 DCP lieu tiy thiet bj do t i m Wi-Fi Khi t h i i t bl dd tim Wi-Fi b i t dugc tin hieu ciia mot t h i i t bj di ddng thdng minh dang bat e h i do Wi-Fi, nd se luu lai dia chi MAC address ciia t h i i t bl Vi MAC address la mgt gia trj duy n h i t va khae biet giu'a cac t h i i t bi di dgng thdng minh, nen khi ngudi tham gia giao thdng e l m t h i i t bj nay di chuyen tren d u d n g , hanh trinh eua ngudi nay ed the se d u g c ghi lai b i n g cae t h i i t bi dd tim Wi-Fi dat tren t u y i n d u d n g . Qe cd the t i i uu hieu qua eua t h i i t bj dd tim Wi-Fi, thu nghiem thye t i cung n h u nhirng nghien cuu trudc day
ciia Musa (2011) hay Abedi (2015) d i u eh! ra r i n g , khoang each giira hai vi tri dat t h i i t bj khong nhd han 200 m,
Du' lieu t h i i t bi dd tim Wi-Fi cung cap ba thdng tin quan trgng co y nghTa giao thdng, bao gdm MAC address, vi tri MAC address nay duae ghi nhan (trong trudng hgp nay ia vj tri dat thiit bi dd tim Wi- Fi), thai diem MAC address nay duae ghi nhan. Bang phuang phap k i t noi cae vi tri va thai d i i m cd eiing MAC address, hanh trinh dl c h u y i n eua ngudi tham gia giao thdng se duae ghi lai va thai gian di chuyen giua cac cap d i i m dat thiit bj dd tim Wi-Fi cung se d^saz tinh toan
2.2 P h i r a n g phap xac d m h t h a i gian di chuyen
Phuang phap xac djnh thai gian di c h u y i n bang thiet bi dd tim Wi-Fi bao g i m hai bude ehinh: tinh toan thdi gian di chuyin va hieu chinh so lieu
Khi mdt ngudi d i i u kbiin phuang tien giao thdng cam dien thoai thdng minh di qua t h i i t bj dd tim Wi-Fi d vi tfi I va J, thai d i i m nay se d u g c ghi !ai tuang irng la t , ; t^,; t^; . va t ; t^^, t^-,... Trpng s i nhirng thdi diem nay, thdi d i i m dau tien va e u i i eung hay thdi diem khi phuang tien vao va ra khoi pham vi boat ddng ciia t h i i t bi dd tim Wi-Fi la rat quan trpng. Theo nghien eiru ciia Abedi (2015), khi tfnh toan thai gian di c h u y i n dya vao cac thdi diem d i u tien va c u i i ciing nay, ket qua eudi eung cd do chinh xac cao n h i t Vi vay, nghien ciru sir dyng
b i n cong thuc de xac dinh thdi gian di chuyen nhu d u d i d a y
^...»t. = K.,..-K.,. (2)
Trong dd f ^^^^^, va (^„,^, la thdi diem dau tien d u p e ghi lai cua mgt MAC address tai vj trf dat t h i i t bj dd tim i va j ; edn t ^^^^ ^ va (^^,, la thai d i i m e u i i ciing d u a e ghi lai
Qua trinh hieu ehinh sd lieu la rat can t h i i t vi thdi gian di chuyen sau khi d u g c tinh toan v i n t i n tai n h i i u gia tri bat thudng cd the khdng phan anh dung thai gian di chuyen thuc te tren doan t u y i n Vf dy nhu xe u u tien se cd thdi gian dl chuyen nhanh ban binh thudng, trong khi mgt phuang tien dirng giua Vj tri dat hai t h i i t bi dd tim Wi- Fi d i mua sam, an u i n g hoae lam viec r i i mdi di chuyen t i i p se khiin cho thdi gian di chuyen giira hai diem ldn bat thudng
Goi p^g^ la t i c dp toi da phu hap ma eac phuong tien ed t h i di chuyen d u a c tren doan tuyen (dan vi s/m), Cd the t h i y p^^^phu thuoc vao yeu t i eua d u d n g va tinh hinh giao thdng thuc t i . Vi vay, nghien ciru nay se xac dmh p^^^dya vao thanh phan van tdc ciia cae xe chay tren eting doan t u y i n theo cdng thirc:
Pm.,. = T>..„e,ce.,i,e ' ^ ' ( ^ ) Trong dd p^ groemie '^ '^"^ ^^ '^^^ ^ phan tram ngudi di chuyen nhanh n h i t va e la gia tri tuy chinh. Ca e va X se d u g c xac dmh b i n g phan tich do nhay trong phan 4
Scaiynerj ^ n
Hinh 1. Xac dmh thai gian di chuyin bing thiet bi dd tim Wi-Fi
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2.3. Kiem tra do chinh xac cua viec xac djnh th6<i gian di chuyen D e kiem tra dp chinh xac khi xac djnh thdi gian di chuyen b i n g t h i i t bi dd tim Wi-Fi, nghien eiru t i i n hanh sp sanh gia trj nay vdi gia tri xac dinh b i n g GPS eiia xe khao sat chay tren cung t u y i n d u d n g . N g u d i lai xe khao sat se cam mot thiet bl dl dpng d u g c xac dmh trudc MAC address, cung n h u t h i i t bi ghi lai toa dd thong qua GPS. Tir do, cd t h i so sanh d u g c hieu qua ciia p h u a n g phap nay vdi phuang phap xac dinh thai gian di chuyen t r u y i n t h i n g la GPS
3.THirCHGHIEM 3.1. Gio-i thieu t h y e nghiem Thye nghiem d u a c t i i n hanh trong ba ngay lam viec lien t i i p doe true d u d n g Nguyen Trai - Tay San, Ha Npi, Day ia true d u d n g quan trgng n i l trung tam thanh p h i va khu v y c tay nam dang d u g c d i u t u , phat then manh trong thdi gian gan day.
Bay t h i i t bi dd tim Wi-Fi d u a c dat doc t u y i n d u d n g vdi khoang each tu giira hai thiet bj dau tien va cudi ciing la 5.795 m, n h u hinh 2. Hai may quay cung d u g e dat de kiem tra luu l u p n g giao thdng doc true d u d n g , tir dd ed the tinh d u p e hieu s u i t thu thap du" lieu ciia t h i i t bj dd tim Wi-Fi. T h y e nghiem d u a c t i i n hanh lien tuc tir 7 gio' sang d i n 20 gid moi ngay d i ed the thu thap dCi' li#u giao thdng khdng chi vao hai khung gid cao diem trong ngay, ma
r i - F 2 1-2 PJ IM-P4 P 4 - B \
n\-\
U . A 2 112-1 m 9 S 4 m 915 IB 782 m 653 oi 1365 n.
con lay d u g c du' lieu vao khoang thdi gian t h i p diem.
De t i i n hanh kiem tra do chinh xae ciia viee xac dinh thdi gian di c h u y i n b i n g t h i i t bi dd tim Wi- Fi, nghien ciru sir dung m u d i xe khao sat chay dpc t u y i n d u d n g , Mdi xe khao sat ed mpt t h i i t bj di dong d u p e xac djnh trude MAC address, va t h i i t bj nay cung cung c i p tpa dp eiia xe mdi 5 giay. Tir dd. thai gian di c h u y i n eiia cae xe khao sat tren t u y i n dudng se d u p e tinh toan va so sanh vdi k i t qua ciia t h i i t bj dd tim Wi-Fi 3.2. DO' lieu thu thap Trong ba ngay thye nghiem, so lugng d\x lieu thu thap dupe bdi t h i i t bi dd tim Wi-Fi l i n lupt la 950.457, 947,327 va 912 592, t u a n g d u a n g vdi m i l t i i n g thu thap d u a c tren 80,000 tin hieu.
Them vao dd, 147 hanh trinh di chuyen eiia xe khao sat d u g c ghi nhan d i s u dung eho qua trinh kiem tra dp chinh xac eiia t h i i t bi dd tim Wi-Fi,
s i luang tin hieu thu thap duge bo'i thiet bj dd tim Wi-Fi trong mdi 15 phut d u a c bieu dien qua hinh 3, Cd the thay lugng tin hieu thu thap d u a c da chf ra dien bien giao
thong thuc te tren true d u d n g , vdi hai khung gid cao diem sang va chieu tuang ddi rd rang Them vao dd, sd lugng hanh trinh di chuyen giQ'a VI tri hai t h i i t bi dd tim Wi-Fi lien t i i p d u a c tong hap qua hinh 4 cho t h i y giao thdng di tir trung tam ra khu vye ngoai thanh nhieu ban vao khung gid cao diem c h i i u , vdi c h i i u ngugc lai thi nhieu han vao khung gid cao diem sang. Ngoai ra, cung cd the thay sd lugng hanh trinh thu thap d u g c theo ca hai c h i i u vao cac khung gid edn lai t h i p han dang k i . Cd the t h i y dCr lieu thu thap b i n g thiit bi dd tim Wi-Fi ed kha nang b i i u d i i n luu lugng thye t i di c h u y i n tren trye d u d n g .
4. PHAH TICH DOT LIEU 4.1 So sanh th6<i gian di chuyen xac djnh ha\ thiet bj do tim Wi-Fi va GPS tii- xe khao sat Tir s i lieu 147 banh trinh ciia xe khao sat, sd lugng hanh trinh tuong irng d u g c trich s u i t tir tep di> lieu cua t h i i t bj dd tim Wi-Fi.
Khi k i t n i l thdi gian d u a c ghi lai eua t h i i t bi dd tim Wi-Fi vdi thai gian ghi lai b i n g GPS, vj tri chfnh xae hay khoang each lir tho'i d i i m nay den vi tri dat t h i i t bj dd
Hinh 2. Mo ta thwc nghiem
I Sd 3 nam 2020
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MMMM KHOA HOC - CONG NGHE
tim Wi-Fi cd the d u g c xac dinh, Hinh 5a va 5b chf ra rang, gia tn trung binh khoang each eiia thai diem d i u tien va c u i i eung d u g c ghi lai bai t h i i t bi dd tim Wi-Fi la -87,4 va 8,9 m, D i u am b i i u thi vi tri ciia phuang tien d trude vi tn t h i i t bl dd tim Wi-Fi theo hudng di c h u y i n . Hinh 5e va 5d bieu thi khoang chenh thdi gian giOa thdi d i i m dau va cudi duge ghi nhan so vdi thai diem di qua vj tri dat t h i i t bi dd tim Wi-Fi. Cd the t h i y day la mgt gia tr; tuang ddi ldn, tuy nhien do lech chuan khoang each va thai gian ciia thdi diem dau tien va c u i i cung lai tuang doi hep, Vi vay, kbi xac dinh thdi gian di chuyen dua vao cdng thirc (1) va (2) se dua ra gia trj chinh xac han cdng thirc (3) va (4) vi do tech se bi triet tieu t u a n g u'ng.
S a n g 1. So sanh thai gian di chuyen cua 4 cdng thirc so sanh
vai ket qua tii' GPS
Enter - Enter Exit- Exit Enter - Exit Exit - Enter
Dd khac biet trung binh (s) 4 5 3.9 35 9 -27,9
Do lech chuan ciia do
khac bi^t (s) 21,8 36 2 37.4 23.6 Bang 1 trinh bay ketqua so sanh s u khae biet giira thai gian di c h u y i n s u dung thiet bi dd tim Wi-Fi va k i t qua tir GPS. Cd the t h i y k i t qua tinh toan b i n g cdng thii'c (1) va (2) cho gia trj dd khac biet tuang doi nho ( d i u d u d i 5s), Vi vay, cac k i t qua thdi gian di c h u y i n tfnh b i n g hai cdng thii'C nay duge su' dyng trong p h i n hieu chinh sd lieu phia d u d i
4.2. Hieu chinh t h a i gian di chuyen K i t qua thdi gian di c h u y i n cua t i t ca eae hanh trinh thu thap d u a c trong thye nghiem d u g c tinh toan d y a vao edng thue (1) va (2) Hinh 6 mo ta thanh p h i n thai gian di chuyen nay, Cd the thay, do edn t i n tai n h i i u hanh trinh co thdi gian di chuyen dai b i t thudng, nen hinh ve cd p h i n dudi dai b i t hgp Ii.
'Li.'Li
a. Sw khac biet vi khoang each b. Sw khac biet ve khoang each cua thdi diim diu ciia thdi diem cuoi
1 6. Thanh phan thdi gian di chuyin
c Sw khac biet vi thai gian ciia d Sw khac biet ve thdi gian cua thai diim diu thai diem cudi Hinh 5. Thai gian va khoang each giiia thai diim diu va cuoi duac ghi nhan bdi thiit bi dd tim Wi-Fi va thdi diem thwc ti xe khao sat di
qua vl tri dat thiit bi | Qua hinh 7, cd the t h i y thdi gian di
chuyen trung binh (dudng mau do) cao han gia tr; thai gian di chuyen p h i b i i n ( m i i n gia tri dam), do ton tai nhieu thdi gian di chuyen dai b i t thuo'ng. B i n g each phan tich dp nhay qua cdng thirc (5), nhirng hanh trinh di c h u y i n b i t hpp Ii se bl loai bd
Hinh 8 md ta thanh phan t i c do (dan vi s/m) d u a c ghi lai. Cd the t h i y 10% nhirng lai xe cd toe dd di chuyen nhanh nhat ciia eac doan t u y i n cd t i c do di c h u y i n tuang d i i gidng nhau, trir doan A1-A2, chirng td rang doan A I -A2 la doan t i e n h i t tren ca tuyen. Hien tugng lai xe c i n n b i i u thai gian ban de di h i t I m dudng b i t d i u x u i t hien d gia trj 0,4 s/m va d i i vdi doan A 1 - A2 la tir'0,5 s/m.
K i t qua phan tich do nhay nhu hinh 9 cho thiy, vdi gia tn a = 5%, khi dat gia tri e qua nhd, se cd the cat dl nhCrng gia tn thai gian di chuyen hgp Ii, edn kbi dat gia tn e qua ldn se khong xoa d u p e h i t cac gia trj thdi gian di chuyen b i t hgp Ii. Gia tri e phii hgp n i m trong khoang tir 0,3 d i n 0,5 va d u g c xac djnh tuy vao dieu kien eu the a. From P2 to P3
b. FromAI toA2 Hinh 7. Thdi gian di chuyen
trong ngay
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5. KET LUAH
Nghien eiru eho t h i y viec sir dung thiet bi dd tim Wi-Fi d i thu thap dCr lieu giao thdng trong dieu kien ddng bdn hgp d Viet Nam cd t h i mang lai hieu qua tdt. Thdi gian di chuyen xae dinh bdi t h i i t b| nay ed dp chenh lech nhd so vdi thdi gian xac dmh b i n g phuang phap GPS Thdi gian di chuyen tren doan tuyen cd the d u a c xac dmh true quan (Hinh 11), phuc vu cho viec dieu khien giao thdng.
Trong l u a n g lai, nghien ciru se duge t i i p tyc phat trien d i cd t h i ap dung khdng chf tren mdt true d u d n g ma la mdt mang ludi d u d n g de ed the ve ra d u a c thdi gian di chuyen theo thdi gian thye cho eac doan t u y i n , gdp phan cung c i p dd' lieu giao thdng cho ngudi lai xem
' a = 5% va e = 0.4 f. a = 5% va e = 0.45 Hinh 9. Hieu chinh sd Heu vdi a = 5%
Hinh 11. Thdi gian dl chuyen tren true dwdng
TAI UEU THAM KHAO
Abedi. N,. Bhaskar, A., Chung, E„ Miska, M , 2015 Assessment of antenna cliaractenstic effects on pedestrian and cyclists travel-time estimation based on Bluetooth and WiFi MAC addresses Transp Res Rec Part C 60, 124-141 Khan, 8, and Maini, P., 1999 Modeling heterogeneous traffic flow, Transp Res Rec 1678, 234-241
Kiran, M. S , Verma, A., 2016, Review of Studies on Mixed Traffic Flow: Perspective of Developing Economies. Transp in Dev Econ 2 (1).
LI, S., YU, H., Yang, K,, Zhang, J,, Bin, R,, 2014, Video- based traffic data collection system for multiple vehicle types, lET Intel! Transp Syst 8(2), 164-174,
Mallikarjuna, C , Phanindra, A„ Rao, K., 2009, Traffic Data Collection under Mixed Traffic Conditions Using Video Image Processing. Journal of Transportation Engineenng, 135(4), pp.174-182
Meng, J.P., Dai S , Dong, L and Zhang, J , 2007, Cellular automaton model for mixed traffic flow with motorcycles.
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