Factors increasing the risk for longer heavier goods vehicles using the secondary road network
An LHV, a longer heavier goods vehicle - longer and heavier than the regular ones -, can only use the secondary road network when the local road authority has granted permission to do so. To support the road authorities, CROW Information and Technology Platform for Infrastructure, Traffic, Transport and Public space is preparing a publication containing the criteria which road sections and intersections must meet before permission can be granted. During the preparation several road safety questions came up. CROW turned to SWOV for the answers, and they are given in this report.
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The questions are about the following subjects:
1. risks of overtaking;
2. interaction with vulnerable road users at intersections;
3. suction effect on two-wheelers;
4. risks for moped riders using the roadway;
5. risks at dusk or dark.
These questions aim to get answers about whether LHVs have an increased risk of a crash compared with regular vehicle combinations. Considering the short time limit for the answers, no new knowledge was gathered, but only available knowledge has been used.
First, data was studied on crashes involving regular heavy goods vehicles. These figures show that in 2004 the risk of being a fatality as a crash-opponent in a crash with a heavy goods vehicle was approximately 7.5 times higher than that of being a fatality as a crash-opponent in a crash with a passenger car.
In urban areas, the fatalities in crashes with heavy goods vehicles are mainly cyclists (almost 70%). In rural areas, most of the fatalities are among car occupants (57%) followed by cyclists (16%). These figures are from 2006.
In the SWOV vision, as formulated in Advancing Sustainable Safety (2005), heavy goods vehicles are not suitable for the secondary road network which is also used by vulnerable road users. In the long term, these heavy goods vehicles, also including LHVs, belong on the main road network to which industrial areas, terminals, etc. are directly connected. The secondary road network should then only be used by lighter heavy goods vehicles that are especially made suitable for urban traffic.
The answers to the five questions are summarized as follows.
1. Risks of overtaking
Overtaking crashes involving heavy goods vehicles are relatively frequent on the secondary road network. The greater length of LHVs increases the risks. It must be concluded that a total overtaking prohibition is desirable when LHVs are allowed on the secondary road network.
2. Interaction with vulnerable road users at intersections
Crashes between heavy goods vehicles and vulnerable road users often occur at intersections because that is where different types of road users mix. Heavy goods vehicles' blind spot is the cause of many casualties when the heavy goods vehicle turns right. Right turns are probably riskier for LHVs than for regular heavy goods vehicles; further study using observations is recommended.
3. Suction effect on two-wheelers
Passing vehicles cause a strong current of air that affects two-wheelers in the roadway or the immediately adjacent bicycle path. Different factors influence the extent to which they are affected. LHVs are not expected to have a different effect than regular heavy goods vehicles.
4. Risks for moped riders using the roadway
On straight roads and intersections, no safety differences are expected for the road safety of mopeds on the roadway. In right curves, the LHV is riskier than a regular heavy goods vehicle for moped riders who are in a position beside the vehicle. Because of its greater length, the LZV cuts off the curve to a larger extent.
5. Risks at dusk or darkness
LHVs have compulsory reflective contour markings at the rear; regular heavy goods vehicles rarely do. This means an advantage for LHVs concerning rear crashes in dusk or in the dark. There is no difference between the different types of heavy goods vehicles concerning the presence of side markings. Therefore, the risk of side collisions seems higher for LHVs when they cross or enter a road in dusk or in the dark. Overtaking an LHV is risky if it has not been noticed that the vehicle is an LHV. The compulsory sign at the rear indicating the vehicle length should therefore also be clearly visible at night.