How should turn lane pavement markings be interpreted in Idaho?

Question

There's a certain intersection in Idaho, USA that's causing confusion for a lot of drivers. As you can see in the photo, the pavement widens near the intersection, as if there should be a right turn lane. But the widening area is marked with diagonal lines. The turn arrows show that the same lane should be used for traffic going straight and turning right. The only lane usage indicators are the pavement markings and traffic lights. There is no additional signage.

Many drivers turn right from the area with the diagonal stripes, and many others turn right from the lane with the right and straight arrows. There's no clear consensus among drivers on how to make right turns here.

I asked the highway department about it, and they said "...even though this area is not specifically striped as a right turn lane (there isn’t enough room to physically stripe a dedicated area for right turning vehicles), drivers who use it as such are acting lawfully." They cited Idaho Code 49-644, which says, "Both the approach for a right turn and the right turn shall be made as close as practicable to the right-hand curb or edge of the roadway."

Their answer could be correct, but it doesn't feel right to me. I was taught to stay off diagonal lines, and to turn where the arrows are. I searched as many places as I could think of, including titles 40 and 49 of the Idaho code, and I couldn't find the specific meanings of turn arrows or diagonal stripes. What is the correct way to turn right at this intersection, and why?

Answer 1

The "definition" of diagonal crosshatches is given in the Manual on Uniform Traffic Control Devices, under §3B.24, which says:

Option: 01 Chevron and diagonal crosshatch markings may be used to discourage travel on certain paved areas, such as shoulders, gore areas, flush median areas between solid double yellow center line markings or between white channelizing lines approaching obstructions in the roadway (see Section 3B.10 and Figure 3B-15), between solid double yellow center line markings forming flush medians or channelized travel paths at intersections (see Figures 3B-2 and 3B-5), buffer spaces between preferential lanes and general-purpose lanes (see Figures 3D-2 and 3D-4), and at grade crossings (see Part 8).

Standard: 02 When crosshatch markings are used in paved areas that separate traffic flows in the same general direction, they shall be white and they shall be shaped as chevron markings, with the point of each chevron facing toward approaching traffic, as shown in Figure 3B-8, Drawing A of Figure 3B-9, Figure 3B-10, and Drawing C of Figure 3B-15. 03 When crosshatch markings are used in paved areas that separate opposing directions of traffic, they shall be yellow diagonal markings that slant away from traffic in the adjacent travel lanes, as shown in Figures 3B-2 and 3B-5 and Drawings A and B of Figure 3B-15. 04 When crosshatch markings are used on paved shoulders, they shall be diagonal markings that slant away from traffic in the adjacent travel lane. The diagonal markings shall be yellow when used on the left- hand shoulders of the roadways of divided highways and on the left-hand shoulders of one-way streets or ramps. The diagonal markings shall be white when used on right-hand shoulders.

Guidance: 05 The chevrons and diagonal lines used for crosshatch markings should be at least 12 inches wide for roadways having a posted or statutory speed limit of 45 mph or greater, and at least 8 inches wide for roadways having posted or statutory speed limit of less than 45 mph. The longitudinal spacing of the chevrons or diagonal lines should be determined by engineering judgment considering factors such as speeds and desired visual impacts. The chevrons and diagonal lines should form an angle of approximately 30 to 45 degrees with the longitudinal lines that they intersect.

Idaho adopts this standard, and has not modified it in this area. Idaho statutes 49-801 commands you to "obey the instructions of any traffic-control device placed or held in accordance with the provisions of this title". The pertinent section of MUTCD does not command, is says that you are discouraged from traveling. §49-644 commands you to make the turn "as close as practicable to the right-hand curb or edge of the roadway". You should first obey commands, then I suppose you should take their suggestions.