Conciencia de los usuarios del riesgo en las redes sociales

F2.1: Auxiiary turn lanes

Description Right and left turn lanes on the main road approach are designed to allow traffic that is slowing to turn into a side road, to do so clear of through traffic from behind.

Application Auxiliary turn lanes are installed where the volume of turning and through traffic creates a risk of rear end conflicts that result in rear end collisions or other secondary conflicts due to vehicles avoiding a vehicle that has slowed to turn or is stationary and waiting in order to turn. Guidance on the turning and through traffic volume ranges that should be considered for turn bays is found in the High risk intersections guide.

Right turn bay: SH33 Rotorua District (source : Google Pro licence 2010)

Issues Rear end crashes are the main crash type prevented by auxiliary turn lanes. Rear end crashes rarely result in fatal and serious injury. Turning lanes have the potential to increase crossing and crossing- turning crashes, which are more severe. So it is important to ensure that minor crashes are not prevented at the expense of more severe crashes.

At cross roads, right turn lanes increase the crossing distance and risk of crossing crashes. Where there is significant crossing traffic a roundabout should also be considered. Right turn lanes at t-junctions do not suffer from this problem.

Typically designed left turn lanes increase the severe crash risk to vehicles turning right from the side road, as left turning vehicles using them obstruct visibility to through traffic, and the through traffic speeds are higher. This means that the volume criteria should be higher than for right turn lanes. Where provided, careful design of left turn lanes, islands and limit lines is necessary to preserve visibility from near the limit line.

Turning lanes should be of appropriate length to the need. Hatching, continuity markings, and delineation should be used to ensure the through route is obvious and through traffic is not inadvertently trapped in a turning lane.

Adding turning lanes to existing curves can disrupt the alignment, and the guidance provided by delineation. Curves may also have visibility issues that benefit from longer lane transition lengths (tapers).

Auxiliary turning lanes should not be used in conjunction with passing lanes as drivers are tempted to use them to extend the passing opportunity.

Crash reduction • 25–40% reduction in intersection crashes [3]

• 30% reduction of casualty crashes with construction of right turn (rural) and/or left turn auxiliary lane [79]

• 33% reduction in overall injury crashes [138]

Other benefits • Improved traffic flow and increased intersection capacity

Cost $$

F2.2: Sight distance

Description Sight distance at an intersection is needed to allow traffic to identify safe gaps in the through traffic stream from near the limit line, and to allow through traffic to anticipate and accommodate traffic turning in or out of an intersection. (Further guidance on providing safe sight distance at intersections is contained in the High-risk intersection guide.

Sight distance restricted by vegetation looking from side road onto SH27

Application The following low-cost solutions may be implemented to restore/improve the sight distance at intersections: [80], [83]

• Remove/cut back the vegetation.

• Relocate structures that impede sight distance (signs, safety barriers).

• Flatten embankment or batter.

• Bring forward the limit line, if this can be done safely.

Issues Can be difficult to achieve in rural areas as a low-cost measure due to nature of the road.

It is possible to have too much visibility as well as too little. If drivers approaching from a side road can see traffic on the main road from too far back, they may enter at a faster speed and judge the situation from too far back. They typically fail to notice motorcycles and cyclists. This is a known issue at roundabouts and crossroads.

Crash reduction • 30% reduction in casualty crashes [80]

• 28% reduction in total crashes [11]

Other benefits Improved lighting

Cost $

Treatment life 5–10 years

references and

F2.3: Priority control

Description Priority control is either a stop or give way control at an intersection. Traffic signals, although a type of control, are not commonly used on rural roads and therefore are not discussed in the guide.

Application As stated in the Land Transport Rule: Traffic Control Devices, an intersection that has four or more approaching roadways must be controlled by:

• stop or give way signs; or

• roundabout (appendix D); or

• traffic signal.

Where there are three approaching roadways, then discretion on their use with regards to the function and traffic volumes of the road is considered by the RCA.

Issues • The use of a stop sign where not warranted (ie where there is sufficient sight distance). A stop sign should not be used to reinforce a road hierarchy or as a routine response to an actual or perceived problem as this can decrease the effectiveness of the control type.

• Further analysis on safety performance will be completed as part of the High-risk intersection guide

(currently under development).

Crash reduction • 15% reduction in crashes for give way signs [84]

• 35% reduction in crashes for two-way stop signs at a four-legged cross intersection [84]

• 20% reduction in crashes for a one-way stop sign at a T-intersection [84]

Other benefits Improved traffic flow (may also be a cost due to increased delays to major road flow)

Cost $

Treatment life 5–10 years

references and