1 20 June 2007 i2tern Ålborg Effects of Weather and Traffic controlled Variable Speed Limits in Sweden Gunnar Lind, Movea Trafikkonsult AB
2 20 June 2007 i2tern Ålborg Four type situations Intersections or bus stops Urban motorways with heavy traffic Bad weather or road conditions Vulnerable road users on roadside
3 20 June 2007 i2tern Ålborg E6 Mölndal traffic control
i2tern Ålborg 4 Mölndal Southern border of Gothenburg 2*3 lane Urban Motorway, 80 000 vehicles/day, 4 km Before: 70 km/h fixed speed limit Speed with VSL: 90 km/h in good traffic conditions. 30-70 km/h in dense traffic and congestion Start of operation November 2004 (recommended speed) and February 2006 (controlled speed limits with red ring). Investment 14 mill. Skr (1.5 mill. )
i2tern Ålborg 5 Car drivers experiences - Mölndal 70 % finds the system good the uneven traffic rhythm, the amount of stop-and-gotraffic and the queue lengths are decreasing 50% are more attentive it gives good information about what you can expect further on 30% state that their behaviour has improved maintain longer distance to vehicle ahead more restrictive iin overtaking other cars
i2tern Ålborg 6 Speed changes - Mölndal 100 90 80 70 60 50 40 30 20 10 0 90 90 70 70 70 70 free-flow dense queue formation congestion 70 50 Speeds at the first VSL sign (usual tail of the queue) 70 Fixed Rec VSL Contr VSL Higher speed limit effects average speed with 7 km/h Harmonisation results in higher speeds in dense traffic Queues have been shorter (no congestion at the first VSL sign)
i2tern Ålborg 7 Change in traffic conditions - Mölndal 30% 25% 20% 15% 70 90 90 Traffic state at the first VSL sign (usual tail of the queue) 10% 5% 70 70 0% dense queue formation congestion Fixed Rec VSL Contr VSL Queue formations when 30 km/h should have been switched on have not occurred at all during the measured period Queues are less frequent and shorter (closer to Gothenburg)
i2tern Ålborg 8 Safety effects - Mölndal 20% reduction of injury accidents with recommended speed limits 40% reduction of injury accidents with controlled speed limits The reduction is not statistically proven. We need two more years of statistics. The fear for more accidents because of the increase of the speed limit during free-flow cnditions seems to be exaggerated
i2tern Ålborg 9 Conclusions Traffic Control on urban motorways Implementation of VSL seems to be profitable also on urban motorways with low posted speed Acceptance for VSL is very high. Queues leading to big delays have been shortened Accidents have decreased despite higher posted speed in free-flow conditions
10 20 June 2007 i2tern Ålborg E6 Halland weather control
i2tern Ålborg 11 Halland Southwestern part of Sweden 2*2 lane Motorway, 55 km, 20000 vehicles/day, 20% trucks Before: 110 km/h fixed speed limit Speed with VSL: 120 km/h in good weather conditions. 60-110 km/h in bad weather conditions (friction= 0.4 to 0.1) Start of operation July 2005 Investment 36.5 mill. Skr (4 mill. ) Semi-automatical system with TCC approval of speed limits
i2tern Ålborg 12 Car drivers experiences - Halland 90 % finds the system good, 50% even very good 80% are more attentive to the condition of the road surface 70% state that their behaviour has improved more concentrated on driving maintain longer distances to vehicles ahead more restricitve in overtaking other cars
i2tern Ålborg 13 Speed changes - Halland Small effect of higher speed limit (+1,2 km/h) Almost no effect of VSL in wet and snowy conditions VSL stimulate drivers to slow down in severe conditions
i2tern Ålborg 14 Safety effects - Halland VSL has a minor role in wet and snowy conditions, which can be observed by the driver The major role of VSL is in severe weather conditions (very slippery or icy, f=0.1-0.2); VSL stimulate drivers to slow down Theoretical caclulation indicate 10% drop in injury accidents for a well-functioning system Trimming of the system is necessary - speed limit changes are delayed, low speed limits are underutilised
i2tern Ålborg 15 Conclusions Weather control on inter-urban motorways Implementation of VSL can be profitable on interurban motorways if very severe weather conditions can be handled efficiently VSL influence vehicle speeds substantially during severe or very severe road surface conditions The compliance to the normal speed limit (120 km/h) has been greater Steps must be taken to increase efficiency and automation.
i2tern Ålborg 16 Discussion Weather control on inter-urban motorways Steps taken to increase efficiency and automation Strategic decisions: Introduce automatic activation of VSL for the upper speed limits Test a new sensor (Vaisala camera) for detection of road conditions Change TCC guidelines in order to reduce operator handling time Continued discussion about the accurate configuration inluding complementary text messages