Safety assessment of pedestrian-vehicle interaction at signalized intersections: An observational study

Figures & data

Figure 1. The safety pyramid - interactions between road users as a continuum of events.

Figure 2. Examples of TTC/GAP vs time related to the driver-pedestrian in a) hard-interaction; b) no interaction and c) soft-interaction.

Figure 3. Layout of three intersections selected as case-studies and the analyzed turning maneuvers.

Table 1. Intersection description.

Intersection	Description	Code	Municipality	Vehicular flow (v/h)	Pedestrian flow (p/h)	Green phase (s)	Yellow phase (s)	Red phase (s)	Pedestrian distance (m)	Brance angle (degrees)
1	Viale Vaticano, via Leone IV	SD22	I	330	1005	60	4	30	10.6	81
2	Viale Regina Elena, Viale dell’Università	SD43	II	90	580	53	4	63	10	70
3	Viale Palmiro Togliatti, via dei Meli	SD88	V	50	55	26	4	30	8.3	90

Figure 4. Reference points at intersections and trajectory extraction using the Software Traffic Analyzer.

Table 2. Sample of driver-pedestrian interactions of the intersections.

Turning maneuvrers at the intersection	N. of interactions
Right-turn from via Leone IV to Viale Vaticano	120
Right-turn from via dell’Università to via Regina Elena	70
Left-turn from via dell’Università to via Regina Elena	50
Right-turn from Viale Palmiro Togliatti to via dei Meli	30

Figure 5. Theoretical scheme of driver-pedestrian interaction. The conflict area is represented by the hatched zone.

Figure 6. Interaction patterns for intersection “Viale Vaticano - via Leone IV”, “Viale Regina Elena – Viale dell’Università”, and “via Palmiro Togliatti – via dei Meli”.

Table 3. Interaction severity level of the investigated intersections for right and left maneuvers.

Intersection 1 - “Viale Vaticano - via Leone IV” (right-turn)				Severity (right-turn)
Pattern	Type	N.	%	Safe event	Critical event	Conflict
1	Hard	40	33	6	21	13
2	No interaction	19	16	0	10	9
3	Soft	61	51	0	40	21
Percentage of severity				4%	59%	37%
Intersection 2 - Viale Regina Elena - Viale dell’Università (right-turn)				Severity (right-turn)
Pattern	Type	N.	%	Safe event	Critical event	Conflict
1	Hard	21	18	6	14	1
2	No interaction	38	32	0	22	16
3	Soft	61	51	0	29	32
Percentage of severity				4%	54%	42%
Intersection 2 - Viale Regina Elena - Viale dell’Università (left-turn)				Severity (left-turn)
Pattern	Type	N.	%	Safe event	Critical event	Conflict
1	Hard	10	20	5	5	0
2	No interaction	20	40	0	12	8
3	Soft	20	40	0	11	9
Percentage of severity				10%	56%	34%
Intersection 3 - Viale Palmiro Togliatti - via dei Meli (right turn)				Severity (right-turn)
Pattern	Type	N.	%	Safe event	Critical event	Conflict
1	Hard	8	27	2	6	0
2	No interaction	3	10	0	2	1
3	Soft	19	63	1	12	6
Percentage of severity				10%	67%	23%

Table 4. Severity assessment for right-turn/left-turn maneuvers.

	Literature		Method 1 – TTC		Method 2 - PET		Method 3 - TTC + PET
Right Turn	N.	%	N.	%	N.	%	N.	%
Safe event	9	4	12	5	4	2	2	1
Critical event	128	58	76	34	120	55	143	65
Conflict	83	38	132	60	96	44	75	34
Left Turn	N.	%	N.	%	N.	%	N.	%
Safety event	5	10	8	16	0	0	0	0
Critical event	28	56	17	34	30	60	37	74
Conflict	17	34	25	50	20	40	12	24

Table 5. Comparison of the two approaches - right-turn maneuvers.

	Literature(a)	Method 1 – TTC (b)	Correct (c)	False Negative (d)	False Positive (e)	Correct [%] (c/b)	False Negative [%] (d/b)	False Positive [%] (e/b)
Safe events	9	12	9	0	3	75	–	–
Critical Events	128	76	75	53	1	98.7	69.7	1.3
Conflicts	83	132	82	1	50	62.1	0.8	37.9
	Literature(a)	Method 2 – PET (b)	Correct (c)	False Negative (d)	False Positive (e)	Correct [%] (c/b)	False Negative [%] (d/b)	False Positive [%] (e/b)
Safe events	9	4	2	7	2	50	–	–
Critical events	128	120	111	17	9	92.5	14.2	7.5
Conflicts	83	96	80	3	16	83.3	3.1	16.7
	Literature(a)	Method 3 - TTC  + PET (b)	Correct (c)	False Negative (d)	False Positive (e)	Correct [%] (c/b)	False Negative [%] (d/b)	False Positive [%] (e/b)
Safe event	9	2	2	7	0	100	–	–
Critical events	128	143	128	0	15	89.5	0	10.5
Conflicts	83	75	75	8	0	100	10.7	0

Table 6. Comparison of the two approaches - left-turn maneuvers.

	Literature (a)	Method 1- TTC (b)	Correct (c)	False Negative (d)	False Positive (e)	Correct [%] (c/b)	False	False
							Negative [%] (d/b)	Positive [%] (e/b)
Safe events	5	8	5	0	3	100%	–	–
Critical events	28	17	17	11	0	100	64.71	0
Conflicts	17	25	17	0	8	68	0	32
	Literature (a)	Method 2- PET (b)	Correct (c)	False Negative (d)	False Positive (e)	Correct [%] (c/b)	False	False
							Negative [%] (d/b)	Positive [%] (e/b)
Safe events	5	0	0	5	0	–	–	–
Critical events	28	30	27	1	3	90	3.33	10
Conflicts	17	20	17	0	3	85	0	15
	Literature (a)	Method 3- TTC + PET (b)	Correct (c)	False Negative (d)	False Positive (e)	Correct [%] (c/b)	False	False Positive [%] (e/b)
							Negative [%] (d/b)
Safe events	5	0	0	5	0	–	–	–
Critical events	28	38	28	0	10	73.68	0	26.32
Conflicts	17	12	12	5	0	100	41.67	0

Table 7. Variables implemented in the binomial-logistic regression model.

Categories	Variables	Description
Driver-related variables	Vehicular flow	The vehicular flow of drivers who perform the right-turn maneuvers is measured in vehicle/hour along the duration of the video. It is a continuous variable.
Pedestrian-related variables	Pedestrian flow	The pedestrians flow in both crossing directions measured in number of pedestrian/hours. It is a continuous variable.
	Gender	It is a nominal variable divided into two classes for pedestrian gender.
	Pedestrian platoon	The presence of pedestrian platoon isconsidered as at least two pedestrians crossing the road at the same speed. It is a binary variable: 1in the presence of platoons and 0 otherwise.
	Age	It is an ordinal variable divided into age classes: young 0-25 years, adult 26-65 years, and old > 66 years.
Intersection-related variables	Inclination of road segments	The inclination of road segments in degrees. It is a continuous variable.
	Distance of pedestrian crossing	The distance between the pedestrian crossing and the center of the intersection, which is measured in meters. It is a continuous variable.
	Duration of red phase	The duration of the red phase for both users measured in seconds. It is a continuous variable.

Table 8. Correlation matrix.

	Pedestrian platoon	TTCmin	GAPmin	Gender	Age	Vehicular flow	Pedestrian flow	Inclination of road segments	Duration of red phase	Distance of pedestrian crossing
Pedestrian platoon	1.00	0.20	−0.18	0.06	0.01	0.26	0.27	0.01	−0.11	0.25
Gender	0.06	0.07	0.10	1.00	0.00	−0.05	−0.01	−0.11	0.11	0.02
Age	0.01	0.08	0.02	0.00	1.00	0.08	0.00	0.18	−0.18	−0.04
Vehicular flow	0.26	0.04	−0.03	−0.05	0.08	1.00	0.91	0.29	−0.61	0.78
Pedestrian flow	0.27	0.02	0.03	−0.01	0.00	0.91	1.00	−0.13	−0.23	0.97
Inclination of road segments	0.01	0.05	−0.15	−0.11	0.18	0.29	−0.13	1.00	−0.93	−0.37
Duration of red phase	−0.11	−0.06	0.14	0.11	−0.18	−0.61	−0.23	−0.93	1.00	0.02
Distance of pedestrian crossing	0.25	0.00	0.07	0.02	−0.04	0.78	0.97	−0.37	0.02	1.00

Table 9. Binomial logit model.

	β	Odds Ratio (Exp(β))	Sig.	95% Confidence Interval (C.I.) for Exp(β))
				lower	upper
Age	−0.511	0.600	0.05	0.357	1.010
Duration of red (Dr)	0.226	1.026	0.02	1.004	1.040
Intercept	−0.470	0.625	0.517
−2Log L (−2 Log Likelihood Criterion) = 290.039
N = 220; Hosmer Lemeshow goodness of fit Chi^2 (3) =2.073; p-value = 0.557 Model  χ^2 = 11.373, p = 0.003

Figure 7. Probability of conflict related to the duration of red and age classes of pedestrians.