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PDF (DX094490.pdf) - White Rose Etheses Online

PDF (DX094490.pdf) - White Rose Etheses Online

9 They looked also at

9 They looked also at ways of improving further the capacity. Up to then the available ways of improving the capacity of a roundabout was either by increasing its size or by converting it to a multi-level intersection. As both these solutions were very expensive, alternative methods were sought, such that the increase in capacity could be achieved with less expense. One of their observations was that the offside rule improved the performance, and removed locking, even from roundabouts with small central islands. They con- cluded that the major factor controlling capacity was the shape of the junction. Blackmore (1970) observed that roundabout capacity was improved if the diameter of the central island was reduced to one third of the diameter of the circle inscribed within the outer kerb line of the roundabout. The capacity was observed to increase more if the entering traffic was deflected to the nearside which would prevent congestion and allow the central island diameter to be reduced further. The Road Research Laboratory followed the test track experiments by another series conducted on public roads to confirm the above findings. The first test was at Peterborough (Jervis, 1970) in 1968 where signals controlling a junction were replaced by a series of small roundabouts. The observations showed an increase in capacity of up to 23% as the central island diameter decreased and an overall reduction in delay of up to 50%, though delay at peak hour was not reduced as much. In the early 1970 t s further tests were carried out at Colchester,

10 Swindon, Sheffield, Halesowen, Hemel Hempstead and Slough. The findings of these tests are summarized by Blackmore and Narlow (1975). At these experiments several designs were tested including mini, multiple and ring layouts. They all showed improvement in capacity and reduction of delay, ranging from 7% to 35%. Blackmore and Marlow compared the small island layouts to the ring junctions. They concluded that the single island ones are more conventional, simpler in design and installation, easier to be understood by drivers, that they give more capacity for 5-arm sites, greater assurance against locking, higher speeds and lower journey times; ring junctions on the other hand are unconventional and, therefore, difficult to understand, but more safe once familiar, they control speeds at lower levels, and are better for pedestrians. The new layouts have a better safety record where the previous method of control was traffic signals or major! minor priority junctions. However, accidents increase where they replace roundabouts with larger central islands. This was reported by Blackmore and Marlow (1975) and Green (1977). designs. Figures 2.2 to 2.8 show the layouts of the new 2.4 The Need for New Design Formulae The priority-to--the-right rule changed radically the way roundabouts operate. As mentioned before, weaving does not occur any more, the junction resembling a series of linked T-junctions. The new types of roundabouts introduced after 1966 had dimensions outside the limits of Wardrop's formula. However, that formula remained as the official design formula for conventional roundabouts until 1975, although the newer

  • Page 1: A COMPUTER SIMULATION STUDY OF THE
  • Page 4 and 5: 11 SUMMARY This thesis reports on a
  • Page 6 and 7: iv TABLE OF CONTENTS Page No Acknow
  • Page 8 and 9: 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9
  • Page 10 and 11: viii LIST OF TABLES 3.1 Observed Fl
  • Page 12 and 13: 1.1 Roundabout Design 1 Intersectio
  • Page 14 and 15: 3 a modified formula was introduced
  • Page 16 and 17: CHAPTER 2 LITERATURE REVIEW: CAPACI
  • Page 18 and 19: (Wardrop, 1957). The investigation
  • Page 22 and 23: 11 small-island layouts were design
  • Page 24 and 25: 13 operating under no clearly defin
  • Page 26 and 27: where a: the critical gap (sec), NQ
  • Page 28 and 29: where = Q e cx e -1 17 the maximum
  • Page 30 and 31: 19 The research carried out at TRRL
  • Page 32 and 33: take account of local operating con
  • Page 34 and 35: 23 These types are illustrated in f
  • Page 36 and 37: 25 exceeded by a considerable margi
  • Page 38 and 39: 27 queues at the end and beginning
  • Page 40 and 41: 29 TYPICAL CONVENTIONAL ROUNDABOUT
  • Page 43 and 44: EXAMPLE OF GRADE SEPARATED JUNCTION
  • Page 45 and 46: EXAMPLES OF MINI-ROUNDABOUT LAYOUTS
  • Page 47 and 48: "- C) 0 '.-. ) LU 0 S.- 0 C) ( j 0
  • Page 49 and 50: 38 CHAPTER 3 COLLECTION 0F DATA
  • Page 51 and 52: 40 Sheffield. It was observed that,
  • Page 53 and 54: 42 using a SONY AV342OCE portable m
  • Page 55 and 56: 44 Ecciesall Road. However, this di
  • Page 57 and 58: 46 TABLE 3.2 Day Entry Total flow F
  • Page 59 and 60: \\ Ec.esa11 Road \"\\/i? LLjji 1lTh
  • Page 61 and 62: \\\\\ ' \\\\ r * ' \\\_\ ' ' \\% .'
  • Page 63 and 64: 61 CHAPTER 4 GAP ACCEPTANCE CHARACT
  • Page 65 and 66: 63 this field. The conventions used
  • Page 67 and 68: 65 have been developed that use mor
  • Page 69 and 70: 67 of drivers who accept such gaps,
  • Page 71 and 72:

    69 consistently accept all gaps gre

  • Page 73 and 74:

    71 a merging platoon. Although they

  • Page 75 and 76:

    73 They related the gap-acceptance

  • Page 77 and 78:

    75 advance which rejected gaps shcu

  • Page 79 and 80:

    77 proposed by Bennett (1971), Horm

  • Page 81 and 82:

    larger than the respective ones for

  • Page 83 and 84:

    81 The direct linear relationship i

  • Page 85 and 86:

    83 mean squared errors or variances

  • Page 87 and 88:

    85 produce reasonable predictions,

  • Page 89 and 90:

    87 the rejected gaps. The results o

  • Page 91 and 92:

    89 exclusion of top values decrease

  • Page 93 and 94:

    91 definition of gap size as depend

  • Page 95 and 96:

    93 4.5.8 The Effect of Assuming the

  • Page 97 and 98:

    95 demonstrated on Fig. 4.8 and Fig

  • Page 99 and 100:

    97 When the model was validated by

  • Page 101 and 102:

    99 4.8.2.2 The Negative Exponential

  • Page 103 and 104:

    101 0: the proportion of restrained

  • Page 105 and 106:

    103 coefficient of the regression s

  • Page 107 and 108:

    105 From the point of view of which

  • Page 109 and 110:

    107 TABLE 4.1 (continued) No.1 Loca

  • Page 111 and 112:

    Cl U) a) a) 0 I )1) H U) 0 U) a) '-

  • Page 113 and 114:

    1 2 3 4 56789 10 2.95 2.94 2.68 2.9

  • Page 115 and 116:

    Ci) (ii) 0. 113 TABLE 4.7 mean st.d

  • Page 117 and 118:

    1 2 345678 9 0 2.42 2.44 2.50 2.63

  • Page 119 and 120:

    1 2 3 4 5 6 7 8 9 10 2.61 2.93 2.68

  • Page 121 and 122:

    (i) (ii) a 119 TABLE 4.13 mean st.d

  • Page 123 and 124:

    oup 121 TABLE 4.16 no.of entries on

  • Page 125 and 126:

    1 2 3 4 5 67 8 9 10 11 12 13 14 15

  • Page 127 and 128:

    1 2 3 4 5 6 7 8 9 10 125 TABLE 4.21

  • Page 129 and 130:

    4i -1 0 '-I- U-I a) .li.IC 127 E- .

  • Page 131 and 132:

    129 TABLE 4.26 Time interval- (sec)

  • Page 133 and 134:

    No. of passing vehicles 0. 1 2 3 4

  • Page 135 and 136:

    ci) 4) x4-4 ..-..' .,-4 CDV) U H N

  • Page 137 and 138:

    250 200 50 I00 50 135 o i 6 7 8 9 1

  • Page 139 and 140:

    tag ..engfñLf Weaving Width •3/

  • Page 141 and 142:

    0 0 1, 0 C- 4.5 4. 0 3. 5 3. 0 2.5

  • Page 143 and 144:

    3. 5 3. 0 2.5 0 0 2. 0 1.5 141 1.5

  • Page 145 and 146:

    U, II 114 U z isa 114 Ii. z 0 U) (/

  • Page 147 and 148:

    145 CHAPTER 5 THE SIMULATION PROGRA

  • Page 149 and 150:

    147 following a uniform (rectangula

  • Page 151 and 152:

    149 Let F(t) = r, the random fracti

  • Page 153 and 154:

    151 5. Entering or alternatively up

  • Page 155 and 156:

    153 (b) Three initial numbers for t

  • Page 157 and 158:

    155 vehicles are not of such length

  • Page 159 and 160:

    U U, a Ia- LO 0.9 0.8 07 0.5 - 0.4.

  • Page 161 and 162:

    159 CHAPTER 6 RESULTS AND COMMENTS

  • Page 163 and 164:

    161 equivalent to the capacity of a

  • Page 165 and 166:

    163 parameters. It was found that a

  • Page 167 and 168:

    165 least 50% straight ahead traffi

  • Page 169 and 170:

    167 left-turning vehicles, is not u

  • Page 171 and 172:

    169 exhibit a minimum average delay

  • Page 173 and 174:

    171 not operating at or near capaci

  • Page 175 and 176:

    Input 500 1000 1500 2000 2500 3000

  • Page 177 and 178:

    4000 3500 3000 L 2500 N -c > ..2000

  • Page 179 and 180:

    177 1. Ashworth and Laurence (1977)

  • Page 181 and 182:

    (0 C -J Lj_ o L 0 -a 3 z > 4.0 3. 5

  • Page 183 and 184:

    C.. -C N-c > 1000 980 960 940 920 9

  • Page 185 and 186:

    0 1 U- uJ 540 520 500 480 183 0. 0

  • Page 187 and 188:

    N > 0 -J IL > C- C ILl 0 200 160 16

  • Page 189 and 190:

    C) Co 6 4 >2 -J a m C.. 0 > -I 8 18

  • Page 191 and 192:

    C, Co >\ CD 0 CD CD S 15 10 189 % S

  • Page 193 and 194:

    C) •1 > 0 L. > 10 5 191 ST 101 =

  • Page 195 and 196:

    U (0 >.' -J C, (I > -J 20 10 193 %

  • Page 197 and 198:

    ' -J a m C.. > 10 5 195 Qi = 500 ve

  • Page 199 and 200:

    0 CD CD Ii >\ CD CD CD CD C.. CD >

  • Page 201 and 202:

    0 (U (U (U Cj (U (U > -J (U 20 10 0

  • Page 203 and 204:

    0 I. >' Oi C.. > -J 0 '-0 30 20 10

  • Page 205 and 206:

    0 60 40 IT 203 cx = 2.50 sec 500 =

  • Page 207 and 208:

    C) (0 60 40 20 205 02 = 3.50 sec c.

  • Page 209 and 210:

    t!) 60 40 >20 207 Beta 01 = 1000 ve

  • Page 211 and 212:

    0 0 60 40 120 209 Beta Q1 = 3000 ve

  • Page 213 and 214:

    .0 60 40 11 1.5 211 Alpha Q1 = 1000

  • Page 215 and 216:

    C) Co 60 40 20 213 ALpha Q1 = 3000

  • Page 217 and 218:

    215 A computer simulation model has

  • Page 219 and 220:

    217 hou1d. Therefore any change in

  • Page 221 and 222:

    219 Ashworth, R. and M.Z.H. Mattar,

  • Page 223 and 224:

    221 Kirnber, R.M. and E.M. Hollis,

  • Page 225 and 226:

    223 Wagner, F.A., 1966. "An Evaluat

  • Page 227 and 228:

    7 0 4 225 0 4 20 24 F re A. 1 Qb.er

  • Page 229 and 230:

    4-. C'- -7 227 0 4 12 20 24 -. z ec

  • Page 231 and 232:

    DOUBLE PRECISION R INTEGER*4 I A =

  • Page 233 and 234:

    231 GPNO(i13) = GPNO(K3)+1 NOG GPNO

  • Page 235 and 236:

    43 121(SX,A1) 12 IF (A1.GE.AP) AX =

  • Page 237 and 238:

    235 DELY(H2,M3) T3(i12,N3)-121(112,

  • Page 239 and 240:

    82 2 237 sui entries of lane tar

  • Page 241 and 242:

    108 106 CONTINUE 109 CONTINUE DO 10

  • Page 243 and 244:

    CAP CAP+CA(N3) 125 CONTINUE 00 128

  • Page 245 and 246:

    ci) 0 ci) a) '-I 0 a) 0 4-1 in 4-1

  • Page 247 and 248:

    I-i a) 0 ci) a) $4 a) L;l 4-I 0 -'-

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