Module 6 : Traffic Intersection Control

Lecture 31 : Channelization

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Turning Vehicle Templates

In the design of intersections the turning paths of vehicles assumes utmost importance. The turning paths of design vehicles are given in transparent templates such as the one shown in Fig.  and Fig. . These templates are placed over the intersection plan to trace the path of the turning vehicle. Once this is done, proper islands and other traffic control devices can be designed. As per AASHTO, the turning templates are drawn at an approximate scale of 1"=50'. The radius of the template is measured to the outside front wheel path at the beginning of the curve. The design vehicle for the purpose can be taken out of a list of 16 different types of vehicles suggested by AASHTO. The dimensions of some of the design vehicles are given in Table. 1 below. The templates are applied to the layout of intersections and other facilities in accommodating vehicle maneuvers, including driveways, car parking, truck loading and bus terminals.

Table 1: Dimensions of some common Design vehicles

Design Vehicle Type	Symbol	Overall Dimension
		Height (m)	Width (m)	Length (m)
Passenger Car	P	1.3	2.1	5.8
Single Unit Truck	SU	4.1	2.6	9.1
Single Unit Bus	BUS	4.1	2.6	12.1
Intermediate Semi-Trailer	WB-15	4.1	2.6	16.7

Here we shall take the cases of a passenger car (P) and a single unit truck (BUS) as the design vehicles. The various design elements and their dimensions are shown in Fig. 1 and Table. 2 respectively.

Figure 1: Design vehicle Dimensions and Turning Properties

Table 2: Design vehicle Dimensions and Turning Properties for $90^o$ turns

Vehicle		WB					Minimum Turn
Designation	L(m)	(m)	A(m)	B(m)	W(m)	U(m)	U** (m)	FA	RT
							(m)	(m)	(m)
BUS	12.1	7.5	2	2.5	2.6	2.6	4.98	1.25	13
Passenger Car (P)	5.8	3.4	0.9	15	2.1	1.8	2.61	0.6	7.5

The templates were developed to include a variety of angles, with specific configurations for every 30 degrees of turn (30, 60, 90, 120, 150 and 180). By special manipulation of the template, any degree of turning can be produced within an overall range of 20 to 200 degrees. The four variables-vehicle type, turning radius, angle of turn and scale-provide full flexibility in the use of turning vehicle templates for layout and design. To permit greater latitude in maneuvering of buses, single unit trucks and passenger cars, special bar tenders are included, consisting of turning radii in the range of 13 to 50 meters for the first two and 5.5 to 30 meters for the last type of vehicles which are outside the scope of this discussion. The list of templates for bus and passenger cars is shown in the Table. 3.

Table 3: List of Templates

Vehicle Type	Scales	Turning Radius-m	Average Size-cm
	1:250	R= 13 & 18	$20 \times 25$
BUS	1:500	R= 13 & 18	$18 \times 18$
	1:250	R=13 to 50	$20 \times 25$
		Bar Template
	1:250	R=7.5	1 $8 \times 18$
Passenger car	1:250	R=7.5 to 30	$18 \times 18$
		Bar template

The templates for the Passenger Car (P) and Bus are as shown in Fig. 2, 3 below.

Figure 2: Design Template for Passenger Car (P)

Figure 3: Design Template for Bus