CUMPLIMIENTO DEL DB-SE

The MNL models reported in the literature cover a number of investigations of accidents and injury severities (see for example, Kockelman and Kweon, 2002). As discussed above, in relation to the multinomial logit model, it is assumed that there is no natural ordering between the dependent variable’s categories (more than two categories). In this section, the dependent variable has three categories (ROW1, ROW2 and ROW3). ROW3 is considered as the reference category. A total of 942 pedestrian casualties that had resulted from the pedestrian-vehicle accidents that took place at

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signalised pedestrian crossings were extracted. Of those pedestrian casualties that were involved in vehicle-pedestrian accidents at signalised pedestrian crossings, 25.1% have been classified as ROW1, 24.4 % have been classified as ROW2, and 50.5% have been classified as ROW3. Table 6.2 below shows the coefficient’ estimates of the MNL model, the p-values (measure of significance), the ρ2 and the log-likelihood values.

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Table 6. 2: Summary statistics and estimation results of the ROW MNL aggregate model

ROW1 ROW2

Variable Categories of each variable Frequency (%)

Coefficients (p-value) Odds Coefficients (p-value) Odds

Intercept --- ---- -13.42 (0.000) -- -12.68 (0.000) -- Child (0-15) 105(11.1%) 0.56 (0.142) 1.758 -0.17 (0.694) 0.847 Adult (16-59) 731 (77.6) 0.24 (0.436) 1.275 0.23 (0.462) 1.255 Age group Old (60+) 89 (9.4) 0.00 0.00 -- 0.00 0.000 -- Female 327(40.5) 0.35 (0.055) 1.426 0.12 (0.534) 1.122 Gender Male 481 (59.5) 0.00 0.00 -- 0.00 0.000 -- 16-21 79 (8.4) -0.69 (0.117) 0.499 -0.21 (0.656) 0.808 22-59 704 (74.7) -0.62 (0.073) 0.540 -0.05 (0.894) 0.949

Driver’s age group

60+ 54 (5.7) 0.00 0.000 -- 0.00 0.000 -- Night time 271 (28.8) -0.16 (0.478) 0.853 0.21 (0.317) 1.239 Time of accident Day time 671 (71.2) 0.00 0.000 -- 0.00 0.000 -- Crossing 765 (81.2 0.20 (0.468) 1.226 0.25 (0.353) 1.288 Pedestrian movement Not crossing 177 (18.8) 0.00 0.000 -- 0.00 0.000 -- Going ahead 754 (80.0) -0.40 (0.081) 0.668 -0.40 (0.079) 0.673 Vehicle manoeuvre Other 172 (18.3) 0.00 0.000 -- 0.00 0.000 --

Bus and goods vehicles 287 (30.5) -0.40 (0.073) 0.669 -0.28 (0.207) 0.758

Heavy vehicles

other 655 (69.5) 0.00 0.000 -- 0.00 0.000 --

Pelican 232 (24.6) 0.73 (0.000) 2.073 0.02 (0.941) 1.016

Type of signalised pedestrian

crossing Junction 710 (75.4) 0.00 0.000 -- 0.00 0.00 --

One way street 14 (1.5) 15.09 (0.000) -- 13.08 (0.000) --

Dual carriageway 131 (13.9) 13.61 (0.000) -- 12.63 (0.000) --

Single carriageway 794 (84.3) 13.64 -- -- 12.50 --

Type of road

Other 3 (0.3) 0.00 0.00 -- 0.00 0.000 --

1-2 lanes 582 (61.8) 0.19 (0.392) 1.205 0.25 (0.241) 1.290

Width of single carriageway

3-4 lanes 212 (22.5) 0.00 0.000 -- 0.00 0.000 --

Crossing from driver nearside 298 (31.6) 0.27 (0.175) 0.762 0.28 (0.161) 0.756

First impact of pedestrian

accidents Other 644 (68.4) 0.00 0.000 -- 0.00 0.00 --

Weekend 265 (28.1) -0.18 (0.397) 0.833 0.06 (0.768) 1.062

The day of accidents

weekdays 677 (71.9) 0.00 0.000 -- 0.00 0.00 -- Wet 281 (29.8) 0.27 (0.290) 1.307 0.08 (0.749) 1.084 Road condition Dry 658 (69.9) 0.00 0.000 -- 0.00 0.00 -- Fine 783 (83.1) -0.67 (0.327) 0.511 -0.60 (0.377) 0.549 Rain 135 (14.3) -0.61 (0.377) 0.544 -0.76 (0.271) 0.466 Weather other 24 (2.5) 0.00 0.000 -- 0.00 0.00 -- Summary Statistics

-2 Log-likelihood at zero = 1.343E3 -2 Log-likelihood at convergence = 1.279R3 Log-likelihood ratio index (ρ2) = 0.086

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This section provide a discussion of the results of the model. Mainly, the logical signs of the independent variables and statistical significance of them are discussed. The age group has a positive sign in the model. The positive sign for this factors indicates that for a one-unit increase in the age groups (child and adult), it is expected that the relative risk of these groups (child and adult) being involved in an accident in ROW1 is lower than in the other age group. Therefore, the relative risk of being involved in an accident for child and adult groups decreases when these groups cross in ROW1 by exp (0.56 and 0.24) = 1.76 and 1.28 respectively. With regard to occurrence of an accidents in ROW2, the indication of negative sign for child group that the child group in higher risk to be involved in an accident in ROW2 than ROW3. Therefore, the ratio of relative risk of being involved in pedestrian accidents for the child group is increased when the child group crosses in ROW2 by an exp (0.167) = 0.85. On the other hand, the positive sign for the coefficient indicates that adult group is in the lower risk to be involved in an accident in ROW2 than they are in ROW3. The relative risk of being involved in accidents for the adult group decreases when the adult group crosses at the pedestrian crossing in ROW2 by an exp (0.23) = 1.26.

In term of gender group, the positive sign for the coefficient of female group indicates that for a one-unit increase in the female group, it is expected that the relative risk of being involved in a pedestrian accident in ROW1 is lower than it is in the male group. The ratio of relative risk of being involved in an accident in ROW1 decreases by an exp (0.36)=1.43. Moreover, Table 6.2 above shows that the relative risk for female group of being involved in a pedestrian accidents in ROW2 is lower than it is in ROW3. The ratio of relative risk of being involved in pedestrian accident in ROW2 decreases by an exp (0.12) = 1.12.

Regarding the driver’s age, the negative signs for young drivers (16-21) and adult drivers (22-59) for both ROW1 and ROW2 indicate that for a one-unit increase in these groups, it is expected that the relative risk of being involved in a pedestrian accident in ROW1 and ROW2 is higher than it is in the elderly group. The ratio of the relative risk of being involved in a pedestrian accident in ROW1 increases by exp (0.69 and 0.62)=0.49 and 0.54 respectively and also increases in ROW2, by an exp (0.21 and 0.1)=0.81 and 0.95 respectively.

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night time indicates that for a one-unit increase in night time accidents, it is expected that the relative risk of being involved in pedestrian accidents at night in ROW1 is higher than it is in the daytime. The ratio of relative risk of being involved in accidents in ROW1 increases by an exp (0.16)=0.85. On the other hand, the indication of the positive sign for the coefficient of night time that the ratio describing being involved in accidents in ROW2 decreases by exp (0.22) = 1.23.

Regarding the movement of pedestrians (crossing the road or not crossing), the positive sign indicates that for a one-unit increase in pedestrians crossing the road from the driver’s nearside and offside, it is expected that the relative risk of being involved in a pedestrian accident in ROW1 is lower than it is in ROW3. The ratio of relative risk of being involved in pedestrian accidents for pedestrians crossing the road in ROW1 decreased by exp (0.20) = 1.23. Similarly, the ratio for the relative risk of being involved in pedestrian accidents in ROW2 for pedestrians who crosses the road is decreased by an exp (0.25)=1.28.

In term of vehicle manoeuvres, the negative sign of the coefficient of going ahead indicates that for a one-unit increase in the going ahead manoeuvre in ROW1 and R0W2, it is expected that the relative risk of being involved in pedestrian accidents in ROW1 and ROW2 is higher than for any other manoeuvres. The ratio of relative risk of being involved in pedestrian accidents for going ahead manoeuvre in ROW1 increases by exp (0.40)=0.67 and in ROW2 increases by an exp (0.39) = 0.67.

In terms of the type of vehicle (light vehicles and heavy vehicles), the negative sign for heavy vehicles (heavy goods vehicle and buses) indicates that for a one-unit increase in heavy vehicles in ROW1, it is expected that the relative risk of being involved in a pedestrian accident in ROW1 is higher than for light vehicles. This result reinforces the results of injury severity and heavy vehicles as discussed in Chapter 5. The ratio of the relative risk of being involved in an accident if heavy vehicles are involved increased by an exp (0.40)=0.67. Similarly, the ratio of relative risk of being involved in an accident if heavy vehicles were involved in pedestrian accidents in ROW2 increased by an exp (0.28)=0.76.

Regarding the type of pedestrian crossing facility, the positive sign of pelican, puffin and toucan crossings indicates that for a one-unit increase in accidents that occurred at

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those types of crossings in ROW1, it would be expected that the relative risk of being involved in a pedestrian accident in ROW1 would be lower than for pedestrian accidents occurring at junction crossing areas. The ratio of relative risk of being involved in pedestrian accidents at pelican, puffin and toucan crossings decreased by an exp (0.73)=2.07. Moreover, the ratio of relative risk when an individual is involved in pedestrian accidents at pelican, puffin and toucan crossings in ROW2 decreased by an exp (0.02) = 1.02.

In terms of the width of the single carriageway, the positive sign for one and two lanes on a single carriageway indicate that for a one-unit increase over one and two lanes, it would be expected that the relative risk of being involved in pedestrian accidents in ROW1 is lower than in ROW3. The ratio of relative risk of being involved in pedestrian accidents on one and two lanes of a single carriageway decreased by exp (0.19) = 1.21. The positive sign of the coefficient for one or two lanes in ROW2 indicates that the ratio for the relative risk of being involved in pedestrian accidents on one or two lanes of single carriageway decreased by an exp (0.25) = 1.29.

In consideration of the first impact point in pedestrian accidents, the positive sign indicates that for a one-unit increase in crossing from the driver’s offside in ROW1 and ROW2, it would be expected that the relative risk of being involved in pedestrian accidents in ROW1 and ROW2 is lower than the movement of the pedestrian. The ratio of relative risk when involved in pedestrian accidents for pedestrians who cross from the driver’s offside in ROW1 and ROW2 decreased by exp (0.27) = 0.76 and an exp (0.28)=0.76 respectively.

Regarding the day of the week that pedestrians were involved in accidents, the negative sign indicates that for a one-unit increase in pedestrian accidents that occurred over the weekend in ROW1, it would be expected that the relative risk of being involved in pedestrian accidents in ROW1 is higher than in ROW3. The ratio of relative risk when involved in pedestrian accidents over the weekend increased by exp (0.18)=0.83. On the other hand, negative sign of the coefficient of the weekend indicates that the relative risk of being involved in pedestrian accidents in ROW2 is higher than in ROW3. The ratio of relative risk of being involving in pedestrian accidents over the weekend decreased by an exp (0.06)=1.06.

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In terms of the road conditions, the positive sign for wet roads indicates that for a one- unit increase in pedestrian accidents occurring on wet roads in ROW1 and ROW2, it would be expected that the relative risk of being involved in pedestrian accidents in ROW1 and ROW2 is lower than in ROW3. The ratio of relative risk of being involved in pedestrian accidents on wet roads in ROW1 decreased by exp (0.27) = 1.31 and decreased by exp (0.08)=1.08.

Finally, regarding the weather, the negative signs for fine and rainy weather indicate that for a one-unit increase in pedestrian accidents occurring during fine and rainy weather in ROW1, it would be expected that the relative risk of being involved in pedestrian accidents during ROW1 is higher than for ROW3. The ratio of the relative risk of being involved in pedestrian accidents during fine and rainy weather increased by exp (0.67 and 0.61)=0.51 and 0.54 respectively. Similarly to the ROW2, it expected that the relative risk of being involved in pedestrian accidents in ROW2 is higher than in ROW3. The ratio of relative risk when involved in pedestrian accidents in fine and rainy weather increased by exp (0.60 and 0.76)=0.55 and 0.47 respectively. It should be noted here that the gender, the type of crossing and type of road coefficients were statistically significant in the above models at 95% level. The rest of the variables are not statistically significant.