Trafiksikkerhed i rundkørsler i Danmark - Cykelviden

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46 8. Summary and Conclusions This report is based on accident data extracted from the Danish Road Information System (called VIS). All accidents classified as "accident at a roundabout" are extracted. A total of about 900 accidents from the years 1991 - 1996 are analysed. This includes "injury accidents" and "damage only accidents". So called "extra accidents" are excluded. In the analysis accidents which have occurred on state and county roads are separated from accidents, which occurred on local roads. This is because it has been possible to create a data file containing roundabouts on state and county roads. For each of these roundabouts data about the geometric layout and motor vehicle traffic entering the roundabout from each arm is registered. Bicycle and pedestrian traffic is not registered. Such data on geometric layout do not exist for local roads so only limited analyses may be carried out for the roundabouts on local roads. Results Accident rates for 1991 - 1996 - accidents per million entering motor vehicles - indicate a reduction in the accident risks compared to the rates found earlier for the years 1985 - 1990. Injury accident rates for 1991 - 1996 are near 0,05 accidents per million entering vehicles for different categories of roundabouts both in rural and in urban areas. Similarly, accident rates are about 0,15 for all accidents. Table 8.1 Accident rates Accident rates are accidents/all accidents per million entering motor vehicles Urban areas, 50 km zone Rural areas, 80 km zone All accidents Injury accidents All accidents Injury accidents 3-arm roundab. 0,12 0,04 - - 4-arm roundab. 0,15 0,05 0,19 0,06 5-arm roundab. - - 0,14 0,04 The general accident pattern is essentially the same in 1991 - 1996 compared with earlier Danish studies. Single vehicle accidents is still the largest accident type in rural areas and motor vehicle drivers is the largest category of injured road users (tables 4.8 and 4.9). The injuries in urban areas are dominated by cyclists who most often are injured in collisions with a car that enters the circulation area while the cyclist is circulating past the entry. Accidents in darkness are still of comparatively large importance although less than earlier. An explanation for the change may be that Danish road users have become
more used to roundabouts in general or it may be that the illumination has become better. The analyses can not give the answer. An important reason for this study has been to throw light on the effects of the geometric layout on roundabout safety. The effects of a speed reducing layout of the approaches is illustrated by means of a study of single vehicle accidents in the approaches. A theoretical parameter called "Expected entry speed" or just "Entry speed" is used as a measure for the degree of speed reduction due to the geometrical layout. There are indications in the data that a fairly narrow entry - i.e. strong speed reduction or low "expected entry speed" - lead to increased accident rates in rural areas (80 km/h zone) while the entry speed is of marginal importance in urban areas (50 km/h zone). This dependence on "expected entry speed" is related to single vehicle accidents only and not to accidents between entering versus circulating vehicles. One hypothesis to explain this observation could be that road users' selected speed at the entry is influenced more by the general speed level in the surrounding road network than by the geometry at the entry. However, speed measurements at a number of roundabout entries indicate that the speeds of freely moving vehicles are about the same in urban and in rural areas - about 30 km/h at the give way line - and speeds do not depend on the geometry measured in terms of the "expected entry speed". So far, this problem remains unsolved. Cycle facilities either as a cycle track separated by a curb along the circulation area or as a cycle lane separated by a line marking has been compared with no cycle facilities in the roundabout. No significant differences have been found. The width of the circulation area has no effect on accident rates. This also applies to the diameter of the central island although there is an insignificant tendency to larger accident rates at large diameters (> 30 m). Accident rates for roundabouts have been compared to accident rates for signalised intersections. The comparisons are based on Danish regression models for accident numbers at signalised intersections. It is concluded that on average roundabouts will have slightly fewer accidents than signalised intersections having the same traffic flows. However, differences are small so that a general recommendation of roundabouts in stead of signalised intersection from a safety point of view may not be given. 47
Page 1 and 2: Trafiksikkerhed i rundkørsler i Da
Page 3 and 4: Indholdsfortegnelse 0. FORORD .....
Page 5 and 6: 0. Forord Initiativet til denne rap
Page 7 and 8: Det blev derfor besluttet at gennem
Page 9 and 10: 3. Undersøgelsens data Datagrundla
Page 11 and 12: ovenfor omtalte undersøgelser - li
Page 13 and 14: ektoratets hjemmeside). Denne forsk
Page 15 and 16: 4.2.1 3-benede rundkørsler Der ind
Page 17 and 18: te, at der er sket en reel forbedri
Page 19 and 20: Tabel 4.9 Tilskadekomne trafikanter
Page 21 and 22: hastighed, næst efter trafikmængd
Page 23 and 24: I en ældre engelsk undersøgelse (
Page 25 and 26: Uheldsfrekvens 0,060 0,050 0,040 0,
Page 27 and 28: For uheld af type 8, indkørselsuhe
Page 29 and 30: e end ved større rundkørsler. Ser
Page 31 and 32: 4.5.4 Tilfartshellernes form Ser ma
Page 33 and 34: 5. Resultater for rundkørsler på
Page 35 and 36: direktoratet (litt. 2) førte det t
Page 37 and 38: Tabel 5.6. Uheld af type 1, 8 og 9
Page 39 and 40: 6. Sammenligning mellem signalregul
Page 41 and 42: I tabel 6.2 er ”Stats- og amtsvej
Page 43 and 44: 7. Sammenfatning og konklusioner An
Page 45: fig. 4.3, fig. 4.4, fig 4.5, og fig
Page 49 and 50: 10. Bilag 10.1 Notat fra civilingen
Page 51 and 52: absolut set er relativt lav, regnes
Page 53 and 54: Parallelhelle Begrænsninglinien mo
Page 55 and 56: optræder ved kørsel gennem en for
Page 57 and 58: gennemkørt med samme hastighed. I
Page 59 and 60: Figur 6. Forsætning og længde af
Page 61 and 62: 4. Diskussion af metode Heraf bereg
Page 63 and 64: 5. Henvisninger /1/ Veje og stier.

Trafiksikkerhed i rundkørsler i Danmark - Cykelviden

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