KHOA HOC - CONG NGHE Tap Chf GTVT 10/2009
Xac ajnh kich ihiffic hdp ly cua nhanh din tdi nut giao thong dieu Ichien hdng tin hieu den cl dd thj Viet Nam
Tom tit: M bao irlnh liay pliirflng pliap xac dinh kich thiioc hap l)i ciia nhanh din tdi niit giao thdng dieu lihien hang lin hieu den irong dd thj nildc ta. Ham muc lieu cua hai toan la tdi thieu hoa thdi gian diing chd cua cac xe den nut, tren cd so nghien euu thuc nghiem ve cac dac trung cd han cua ddng xe trong pham vi hoat dpng cua nut: van dgng trUdc khi tdi nut, xep hang chd lin hieu xanh va van ddng thoa! qua niil. Nghien cdu dac diet quan tam ly le xe re trai, cac hinh ihuc re trai cOng nhif quy dao chuyen ddng cua nd. Kei qua la cd sd de xuai md! so giai phap !di uu hda kich ihudc nhanh din nhim nang cao kha nang thdng hanh, chdng un t k va gdp phan cai thien tinh hinh giao Ihdng dd thj hien nay d nudc ta.
Aistpsct: The article presents the method of determining ihe reasonahle dimension oi the leg approach at signalized intersections in urhan Vietnam. Ohjectlve function of problem Is fo minimize time delay of vehicles to the Intersections, on the basis of experimental studies on the basic characteristics ot traffic flows within the signalized intersecflons' operation areas: moving before coming here, lining up waiting green signaf and passing over. The research also interest particularfy in turn left rate, turn left forms as well as ifs moving orbit. As a result, some proposed solutions are optimizing the size of approach, leads to enhance the capacity and combat against congestion and contribute to Improve the urban traffic situation In our country today.
1. DAT VAN OE
Da tu lau v i n d i un t i c giao thdng trong cac dd thi Idn nude ta da trd thanh mdt de tai duoe ca xa hdi quan tam, dUpe coi la mdt van nan tram trpng tdn tai trong ddi sdng xa hdi eua ehung ta. Mdt trong nhung nguyen nhan chinh gay un t i c giao thdng dd thj la do su mat can ddi tram trpng giQa nhu cau di lai dang tang len dot b i i n va kha nang dap ung y e u kem eua he thdng giao thdng dd thi hien tai, Mang ludi dudng phd P cac dd thj ldn ngay eang khdng the kham ndi su qua tai ve phuong tien giao thdng, Vao cac gid cao diem, mat dp tham gia giao thdng tren cae con dudng Idn, nhd la r i t eao, du cae loai xe ldn, nhd chen chue, dan xen vao nhau, nhich tung budc mdt.
Tat ca deu chiu ehung mpt sd phan: ket xe, dac biet la tai cae vi tri nut giao nhau, noi thudng tap trung cae giao c i t , cae diem xung dot, thi hien tupng nay cang trd nen phd bien. Trong nhieu giai phap thiet ke nut giao thdng (NGT), giai phap su dung den tin hieu d i i u k h i i n giao thdng dang trd nen rat phd bien d cac dd thi tren the gidi eung nhu d nudc ta, Giai phap nay
TS. PHAN CAO T H O
Trudng Dai hoc Bach khoa Da Nang
gdp phan tang kha nang thdng hanh ( K N T H ) , giam tai nan giao thdng tai nut va rat phii hpp vdi mdt ddng xe hdn hpp nhieu thanh phan nhu d nudc ta. Tuy nhien vdi giai phap nay, khi thiet ke mdi hay thiet k i cai tao thi h i u n h u eae ky su tu v i n chua cd s u tinh toan cu the nao v i cac yeu td hinh hpc cua nhanh dan d NGT. Day la mpt han che Idn trong cdng tac t h i i t k i qui hoaeh va trong ca qua trinh khai thac NGT, bdi be rdng cae nhanh dan tdi niJt cd vai trd h i t sue quan trpng trong viee hinh t h a n h , dieu tiet va phan tan ddng xe qua niJt, n i u t h i i t k i qua rdng se gay nen su lang phi Idn, cdn neu t h i i t ke qua hep se khdng dam bao luu lUdng xe ra vao nut. Do vay viec t h i i t k i tdi uu kich thudc nhanh dan la mdt ndi dung khdng the t h i i u khi thiet k i NGT,
2. C A C KET QUA N G H I E N CQU
2.1. C d s d ly t h u y e t c u a viec t h i e t ke n h a n h d a n Vdi ddng xe hdn hpp nhieu thanh phan trong dd xe hai banh chiem ty le ldn thi KNTI-I eua nhanh dan phu thudc rat n h i i u vao be rdng eua nd hon la phu thudc vao cae y i u td khac. Vi vay, cd t h i ndi be rdng nhanh dan ia mpt y i u td rat quan trpng quyet dinh d i n sd lupng xe cd the thoat qua NGT ke ca ed hoac khdng cd d i i u khien bang tin hieu d e n , Rd rang trong cung mdt don vj thdi gian, khi be rdng nhanh dan Idn thi lupng xe thoat qua nut ldn va ngupe lai khi be rdng nhanh dan nhd thi lupng xe thoat qua nut se it hon [ 9 ] , [ 1 0 ] , V i n de dat ra la ta can tinh toan t h i i t k i kich thudc eua eae nhanh dan d NGT mdt each tdi uu de vua dam bao kha nang thdng hanh eua nut lai vda dam bao ve mat kinh t i . De giai q u y i t v i n de nay ehtJng ta xem xet bai toan sau [3]:
B a i t o a n : Xet mdt NGT d i i u khien b i n g tin hieu den, gia t h i i t r i n g s u i t ddng tdi da cd the qua vach difng xe ty le vdi cae be rdng B, va B j eua nhanh dan nhu trong hinh 2 . 1 , Mat c i t dupe md rdng tren cac chieu dai L, va L2 du dai cho ddng xe trong hang chd qua dupe niit trong thdi gian den xanh ung vdi NGT dieu k h i i n b i n g tin hieu den theo hai pha.
Gpi Pi va q2 la cac ddng t h i i t k i c i i a eae nhanh dan cd be rdng tuong ung B, va 82 va chieu dai tuong Ling L, va Lg, ehiing ta ed cdng thiic quan he n h u sau:
c X Pi = S X B, X gi (2,1) c X q2 = S X Box g2 (2.2) c X q, = S X L, x g, (2,3) c X q , = S X L2X gs (2,4)
KHOA HOC-CONG NGHE
Trong d d :
S - ddng bao hda cho mdi met rdng ciia mat dudng.
c - thoi gian chu ky (s)
g, va g , - thdi gian xanh cd hieu ciia pha 1 va pha 2 B i i n ddi (2,1):(2,2):(2.3) va (2.4):
Ql + g2
9: + g2
c x q ,
S x B , c xq
S x B , c X q . S x L , S x j . , Vi g . -I- g j = const,
nen dao ham hai ve theo B, va L, se duoc
""1^^ Vl (2,7): ^ ^ V L _ dR, ( u Y dP
(2.5)
(2.6)
J2.8)
'/: 'll
J L
i
<.
^
m,-«
- -
q-
-^-
1 r
Hinh 2.1: So dd thiet lap bai toan
Muc tieu cua bai loan la phai tim tdng be rdng va chieu dai nhanh dan la nho nhat tuong ijng vdi luu lu'ong dong den. nghia la:
dli, dR,
= 0 hay
dU
— - = 0 hay
dR, cl{L -f L )
\ +
•IB.
••] +
dB di
di, ' </!, (//.
Thay (2.7): (2.8) vao (2.9) va (2,10)
1- ' / i 0
' / ; (B, yB,j
111
0 (2.9)
^0 (2,10)
( 2 , 1 1 ;
(2,12)
Tu cong thuc (2.11) va (2.12) ta thay ring, mdt nhanh dan se chiu duoc mot lugng xe Idn gap bdn lan nhanh din khac khi no dai va rong gap dot nhanh dan dd.
2.2. Ket qua nghien cdu
2.2.1. Quan he giua be rdng va chieu dai cua nhanh dan vdi cung mot luu lUgng xe tren hang chd.
Mdi xe trong hang c h d se chiem mdt khdng gian chd Deho - la p h i n dien tich chiem c h d eua mdt xe trong ddng xe d i d a m bao dd an toan. Su d u n g cac gia trj D-,„ tuong ung vdi cac loai p h u o n g tien trong bang sau [4] :
Bang 2.1. Khdng gian chiem chd cua cac xe trong hang chd [4]
r'"~
Loai xe
i
i Kich thude ehd
! (m^/1 xe) Xe dap
2,1 Xe may
2,3 Xe con
11,52 Xe tai
20,16
Xe buyt (loai
>36ehd;
54 cho)
40,32
Ta thay, vdi s u i t ddng d i n nhanh dan la N(xe), se tuong ung vdi mot dien tich cho tdng cdng la:
Fcho = N X Dcr,, = const (m^)
N i u nhanh dan cd be rdng B, chieu dai L thi:
Fcho = B X L > N X Dcho = const ( m ^ ;
N x D .„.
^ L >
(2.13)
B
( m ) (2.14)Nhan xet: Ro rang ta t h i y B va L ed quan he ty le nghjch vdi n h a u , vdi c i i n g mdt luu lupng xe vao nhanh d a n , khi B nhd thi L Idn va khi gia trj B tang d i n len thi L se giam x u d n g . Tuy nhien gia trj B la ed gidi han theo c i p hang dudng va phii hpp vdi thuc t i cua giai phap dieu khien giao thdng b i n g tin hieu den. Trong cac dd thi d nude ta be rdng nhanh dan d NGT D K B T H D thudng khdng vupt qua bdn lan xe vdi gia tri la 15m (tupng iing vdi mdt be rdng ian xe ldn n h i t theo tieu ehuan la 3,75m), Do dd khi t h i i t k i mdi hay t h i i t ke cai tao mdt N G T n i u be rdng nhanh dan tinh ra Idn hon gia trj 15m mdi dam bao luu lupng xe thdng qua niit thi nen nghT d i n cac phuong an phan ludng giam tai t d xa,
Nhu vay ddi vdi mdi N G T , iing vdi be rdng nhanh dan t h i i t k i , se tdn tai mdt chieu dai hang c h d gidi han [L]cho- N h u v a y , neu b i i t dupe luu lupng xe d i n vach dung trong khoang thdi gian t d mpt nhanh dan cd b i rdng B da b i i t , thi se xac dinh duOc chieu dai nhanh dan gidi han L dii de dam bao tat ca ludng xe ehd ed kha nang thdng qua dupc nut,
2.2.2. Trinh tu tinh toan kich thudc nhanh din Budc 1:
Xae djnh c u d n g dp xe tdi niit q . , q , c u a pha 1 va pha 2 trong gid cao diem.
Quy ddi q , , qp ve nam tinh toan tuong lai dupe cae gia tri N,, N2
Ddi vdi cac niit thiet ke cai tao, vie-c xae dinh q,, q j c o the thuc tiien dupc b i n g each r, xe true t i i p hoac quay camera trong tung khoan-j -5 phut m d t d gid cao diem.
KHOA HOC - CONG NGHE Tap chi GTVT 10/2009j^J|
Budc 2:
Lap ty s d 7_
Ta cd cae k i t qua sau:
B.
(I vaa X Lp
Hoac P, =1315 X B, -^ Bl = a X B2 va Ll Bivdc 3:
Tinh b i rdng nhanh dan: L i n lUdt thay B, bang cac gia trj tu (3m -=-15m), ta se ed eae gia trj tuong ung B,, liie nay k i t qua tdi Uu eiia B, va Bg se la eae gia tri vua dam bao (B, va B2),„in vda dam bao thda man d i i u kien v i miic phuc vu ciia N G T D K B T H D [4], [5]:
yV, N.
Pi = 395 X Bl > — - va P2 = 395 x B2 > — ^ ;
z z
xeqd/h
> — ^ va P 2 = 1 3 1 5 x B 2 > — ' - ;
Z Z
xmqd/h
Trong dd: Z la he s d mue dp phuc vu ed the tham khao bang 3-3 [2] va mue phuc vu hieu qua c i i a N G T D K B T H D [5]; B la b i rdng nhanh d i n (m).
Pi va P2 la Kha nang thdng hanh ciia nhanh dan d i n N G T D K B T H D [4], [6],
Ddi vdi eae NGT cd cac nhanh dan vdi b i rdng tii 7m-15m ddng xe hdn hpp dUde ddi ra xe con quy ddi:
P = 395 X B (xcqd/h)
Ddi vdi eae NGT cd cac nhanh dan vdi be rdng tu 3m-10m ddng xe hon hop dude ddi ra xe may quy ddi:
P = 1 3 1 5 x 6 (xmqd/h) Budc 4,-Tinh chieu dai nhanh d a n :
Theo [1], [2] c h i i u dai nhanh dan khdng nhd hon 60m, do dd ta l i n lupt thay L2 bang cac gia tri 60m trd len, ta se ed cae gia trj tuPng dng L i , luc nay k i t qua tdi uu cua Ll va L2 se la cac gia tri vua dam bao (Li va L2)m,n vua dam bao thda dieu kien:
N x D , L > ^ ^ (m)
B
Trong dd: N - s u i t ddng tdi da d i n nhanh dan trong thdi gian ehd.
Dcho - la phan khdng gian c h i i m chd eiia mdt xe trong hang ehd, xac dinh theo bang 2 , 1 .
Nhu vay: Tai NGT dieu khien bang tin hieu d e n , khi biet dUde kha nang thdng hanh thuc t i N, b i i t dupe loai dudng va tdc dp t h i i t ke eua cae n h a n h dan, ta se tim dupe b i rdng va chieu dai eua cac nhanh d i n d d , Cac gia trj nay se dam bao kha nang thdng hanh va dam bao dat cac gia trj tdi uu.
3. KET L U A N :
1, P h i n ldn kich thudc nhanh dan d cae NGT trong cac dd thi nude ta deu dupe thiet ke b i n g kich thudc eiia cae t u y i n dudng ngoai niit, cac gia trj nay d i u tuan theo eae tieu ehuan, qui pham. Tuy nhien N G T la mdt noi tap trung lupng xe rat Idn vdi n h i i u
diem xung dot muc dp khac nhau, viec cau tao nhanh dan cd anh hudng rat ion den su van ddng eua ddng xe, Vi vay de thiet ke cau tao nhanh dan hop ly ve vi tri va kich thudc n h i m tang kha nang thdng hanh va an toan xe chay can phai nghien euu nhieu hPn ve ddng re trai, re phai va chieu dai hang c h d [7], [8],
2, Tren co sd ciia giai phap tim tdng be rdng va chieu dai ciia cac nhanh dan la nhd n h i t ung vdi s u i t ddng Idn nhat, ddng thdi ap dung cac k i t qua nghien euu ve KNTH cua nhanh dan toi N G T D K B T H D d d i i u kien giao thdng dd thi nude ta [6], de giai quyet bai toan tdi Uu hda kich thudc nhanh dan d NGT d i i u k h i i n b i n g tin hieu d e n .
3, Sau khi tinh toan va lua chpn dUPc gia trj be rdng eung nhu c h i i u dai ciia cac nhanh dan d NGT mpt each hop ly theo 4 budc d tren, t i i n hanh d i x u i t mdt sd giai phap t h i i t k i cau tao kich thude nhanh d i n n h i m phii hpp vdi dieu kien giao t h d n g , dieu kien dja hinh cua nut va dae biet n h i m han e h i tdi da cdng tac den bii giai tda mat b i n g - cdng tae lam tieu tdn nhieu thdi gian va t i i n bac trong khi xay d u n g ,
4, Tuy nhien cung can luu y r i n g , khi mdt nhanh d i n duoe tinh ra ed kich thudc nhd hon cae phan xe chay tdi thieu thuc t i thi phai tham c h i i u T C X D V N 104-2007 de lua c h p n . D
TAI LIEU THAM KHAO
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[2]. CHXHCNVN (2007), Dudng do thi - Yeu cau thiet ke TCXDVN 104-2007, NXB Xay dung
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[7]. Phan Cao Thg (2009), "Anh hudng ciia xe re trai den kha nang thong hanh ciJa NGT dieu khien bSng tin hieu den d do thi Viet Nam". Tap chi Khoa hgc & Cong nghe cac trudng Dai hgc Ky thuat so 69/2009, trang 71-75,
[8]. Wolfgang S, Terome W. Hall, Roy C.
Loutzenheiser (1995), Fundamentals of traffic Engineering.
University of California, Berkeley,
[9], James H. Kell; Iris J. Fullerton (1998), Manual of Traffic Signal Design, Institute of Transportation Engineers, Washington D.C.
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Elements de theorle du Trafic et applications. Paris
