PROVISION OF A LEFT SLIP LANE TO THE NORTHERN SECTION OF THE HAASENDAL DEVELPOMENT, KUILSRIVIER

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1 Date: 10 August 2016 Contact: Liezl du Plooy (tel ) Our ref: D122 Transport for Cape Town PO Box 19 Somerset West 7129 Attention: Mr. Bill Jones Sir PROVISION OF A LEFT SLIP LANE TO THE NORTHERN SECTION OF THE HAASENDAL DEVELPOMENT, KUILSRIVIER Our previous correspondence and discussions regarding the possible provision of a left turn slip lane from Saxdowns Road southbound onto the northern section of the Haasendal development in Kuilsrivier refer. Deca has done a detail investigation of the impact of a left turn slip lane, including the impact on traffic flow on Saxdowns Road and at nearby intersections. The Western Cape Road Access Guidelines recommendation of a maximum of 300 vehicles per hour allowed via a left in / out access was also researched and is discussed in this letter. 1. BACKGROUND The Haasendal development proposal is more than 10 years old and a number of changes have been made over the last few years. The latest proposal as workshopped with City of Cape Town planners proposes a densification in the residential components of the development, as well as increased commercial space. A full transport impact assessment will be done for the new proposal and therefore only the main traffic facts and figures are given here. The July 2016 development proposal entails a commercial component of m 2 GLA, a school for an estimated 500 learners and 3211 residential units. Allowing for dual purpose and by-pass trips, it was calculated that the development would generate 3989 new, external trips during the AM peak hour (1128 in, 2862 out) and 4459 trips (3121 in, 1337 out) during the PM peak hour. For the purpose of the TIA it was assumed that the portions north of the Bottelary River, which roughly bisects the site, will obtain access via the northern entrance(s) to Haasendal, with the portions south of the river making use of the southern Haasendal entrance. It was calculated that the northern portion would generate approximately 40% of the total Haasendal trips with the majority of trips coming from the north. 2. ACCESS TO THE NORTHERN SECTION The original transport impact assessment, which was based on fewer trips, indicated that only one access would be provided to the northern section. The developer is now requesting that an additional entrance be considered in the form of a left turn slip lane approximately 150 metres

2 north of the approved northern Haasendal entrance. The 2002 Road Access Guidelines (Table 5.5(a)) differentiates between low- and high generator driveways, equivalent local distributors and equivalent district distributors. In suburban environments such as the Haasendal area, the threshold for equivalent local distributors is 100 vehicles per hour (125 for intermediate) and for equivalent district distributors it is 300 vehicles per hour (375 for intermediate). The expected number of trips on the proposed slipway will be between 178 vehicles per hour (vph, for filling station access only) and 852 vph (75% of trips generated by the northern section and coming from the north). From the expected volumes it is clear that the slipway will be considered as an equivalent distributor (local or district) and that an intersection with a Class 3 road is therefore allowed. According to Table of the 2002 RAG, the normal minimum value for the spacing of an equivalent Local Distributor access in a suburban environment is 180 metres for a full access and 120 metres for a left only access. 3. TRAFFIC IMPACT In order to evaluate the impact of the proposed slip lane, the other intersections that will be impacted by the presence of the sliplane were analysed. The alternative route for traffic to and from the north en route to the northern Haasendal section is via Saxdowns Road southbound onto Pugsli Road eastbound and from there northwards at the first side road (called Road in the rest of the document) and from there either to the west (filing station site), north (shopping centre) or east (residential developments). The intersections on this route were analysed with different traffic volumes on the slip lane (see Tables 1-3, attached). Through traffic volumes on Saxdowns Road were estimated at one third of current Amandel Road traffic volumes, as these two roads will serve roughly the same origins and destinations. The volumes used are 966 vehicles per hour (two-way) in the AM peak hour and 882 vehicles per hour in the PM peak hour. Saxdowns Road will have to be dualled in future to accommodate these volumes in addition to future Communicare developments and Haasendal traffic. Saxdowns Road / Pugsli Road (Table 1): The analysis shows that the provision of a slip lane to accommodate traffic from the north en route to the shopping centre will alleviate congestion at the downstream Saxdowns Road / Pugsli Road intersection to the extent that fewer turning lanes will be required. The reduction in left turn traffic on the northern approach allows for longer green time for the right turn movement on the southern Saxdowns Road approach. Delays at this intersection will be reduced further if traffic on Saxdowns Road southbound on the way to the northern Haasendal residential developments are allowed to make use of the slip lane as well. Pugsli Road / Road (Table 2): With only filling station precinct traffic allowed to use the slip lane, the existing stop controlled intersection will be unable to accommodate all the traffic passing through the intersection. By allowing shopping centre traffic to make use of the slip lane, capacity at the Pugsli Road / Road intersection will be increased sufficiently to maintain acceptable service levels on all approaches with stop control. By routing the northern residential area traffic through the slip lane in stead of Pugsli Road, service levels will improve even further. The provision of a roundabout at this intersection was also investigated. The spacing between the Pugsli Road stop line at the Saxdowns Road intersection and the yield line of a possible roundabout at Pugsli / is 60 metres. The Provincial Road Access Guidelines indicates that a 100 metres is required for weaving on a 50km/h road. This standard is for random arrivals that merge upon arrival at and departure from a traffic lane. The traffic stream on Pugsli Road will require a shorter weaving distance due to the fact that vehicles arrive in platoons from the downstream traffic signals and because both eastbound lanes 2

3 have the same destination, therefore vehicles have no need to change lanes before they reach the roundabout. In the westbound direction, weaving can start from the yield line on the eastern Pugsli Road approach, which is located the standard 100 metres from Saxdowns Road. See Diagram 1. A roundabout will operate at a level of service B for the same three scenarios investigated for stop control. The maximum queue length on the western Pugsli Road approach will be 40 metres (7 vehicles) if all the shopping centre and northern residential traffic travel through the roundabout and 12 metres (2 vehicles) if the shopping centre and northern residential traffic is allowed to make use of the proposed left turn slip lane. Diagram 1: Weaving distances on Pugsli Road Road / Filling station access: The original intention was to provide a left in / out access to the filling station off Road, with traffic using the Road / Mall Access roundabout to make U-turns if returning to the south. A left in / out however doesn t allow outbound (southbound) traffic on Road to access the filling station. It is proposed that a right in only, with a tapered right turn lane in the median, be provided on Road southbound. A right turn lane will not be needed if a roundabout is provided at the Pugsli Road / Road intersection. Road / Mall Road / Slip Lane intersection (Table 3): The roundabout at this intersection will operate at a level of service A with no slip lane (slip lane directly to filling station); with shopping centre traffic entering via a one-way slip lane; and with the northern residential traffic added onto the sliplane. The maximum queue length on the Slip Lane approach will be 19 metres (3 vehicles). The analysis shows that there will be more than sufficient stacking space available on the Slip Lane approach to ensure that queuing traffic on this approach does not impede traffic flow on Saxdowns Road. 3

4 4. GEOMETRIC DESIGN The proposed layout of the slip lane to the filling station and northern residential area is shown in the attached Road Layout for Proposed Left In Plan (JVE Engineers Drawing No proposed left in Rev A dated May 2016). This drawing shows that there will be a single left turn slip lane off Saxdowns Road with the taper starting approximately 210 metres north of Pugsli Road. The separation point between the slip lane and Saxdowns Road through lanes will be approximately 140 metres north of Pugsli Road. The drawing shows that the slip lane will split into two lanes where it enters the Haasendal site, with one dedicated lane towards the shopping centre roundabout and a shared lane towards the filling station precinct and the roundabout. The SIDRA analysis shows that only a single lane is required towards the shopping centre roundabout. The lane layout used in the SIDRA analysis is shown in red on the JVE drawing. The slip lane to the filling station precinct has a 60-metre stacking distance measured from the point where this lane splits from the main slip lane. The stacking is more than sufficient. 5. CONCLUSIONS The investigation into the impact of a left turn slip lane from Saxdowns Road southbound to the northern section of the Haasendal development shows that the lane will have a positive impact. The results of the investigation are summarised below: The volumes that will make use of the slip lane is equivalent to those on an equivalent local distributor road (>300vph); The spacing requirement for the equivalent local distributor on a Class 3 road (Saxdowns Road) in a suburban environment is 120 metres for a left only access; The provision of the left turn slip lane upstream from the Saxdowns Road / Pugsli Road intersection will draw the majority of southbound traffic en route to the northern section of Haasendal, with the effect that left turn volumes on Saxdowns Road southbound at Pugsli Road will be much lower. This will give more green time on the other approaches and will mean that fewer lanes would be required to make the intersection work; The existing stop controlled intersection at Pugsli Road / Road will not have sufficient capacity to accommodate all traffic en route to the shopping centre and northern residential areas. The stop controlled intersection will operate at acceptable service levels if most of this traffic is rerouted via the proposed slip lane; Queues on the Slip Lane (western approach) at the Road / Mall Access roundabout will be no more than 19 metres (3 vehicles). There will be more than sufficient stacking space available on the Slip Lane approach to ensure that queuing traffic on this approach does not impede traffic flow on Saxdowns Road; There is sufficient stacking space at the filling station precinct to allow the left turn slip lane off Saxdowns Road to give access to this site too. See the attached Road Layout for Proposed Left In Plan (JVE Engineers Drawing No proposed left in Rev A dated May 2016) with minimum lane requirements shown in red. 6. RECOMMENDATIONS It is recommended that the proposed slip lane off Saxdowns Road to the northern section of the Haasendal development should be approved. 4

5 We trust that this letter gives sufficient motivation for the approval of the proposed slip lane. Kindly contact Liezl du Plooy at telephone number should you have any questions. Yours truly Liezl du Plooy M. Eng Pr. Eng Deca 5

6 Table 1: Impact of slip lane utilisation on Saxdowns Road / Pugsli Road intersection Intersection Condition Intersection layout Service level (existing layout) Service level (improved layout) Improved layout Only filling station precinct traffic through slip lane F, with >500m queues LOS C Saxdowns Road 74 AM 178 PM Shopping centre (N75%) and filling station traffic through slip lane F, with >500m queues LOS D Saxdowns / Pugsli s Road Shopping centre, Northern residential (N75%) and filling station traffic through slip lane LOS F LOS D

7 Table 2: Impact of slip lane utilisation on Pugsli Road / Road intersection (Friday PM peak hour only) Intersection Condition Intersection layout Service level (existing layout) Service level (improved layout) Improved layout Only filling station precinct traffic through slip lane LOS F on eastern Pugsli approach with 156m queue LOS B with max 40m queue on eastern Pugsli approach Road Pugsli Road Shopping centre (N75%) and filling station traffic through slip lane LOS D on eastern Pugsli approach LOS B Pugsli / Road Pugsli Road Shopping centre, Northern residential (N75%) and filling station traffic through slip lane LOS C on eastern approach LOS B Road Pugsli Road

8 Table 3: Impact of slip lane utilisation on Road / Mall Road intersection (Friday PM peak hour only) Intersection Condition Intersection layout Service level (existing layout) Only filling station precinct traffic through slip lane LOS A, max queue 9m Mall Rd Shopping centre (N75%) and filling station traffic through slip lane LOS A, queue on slip road (western approach) 10 metres / Mall Mall Road Shopping centre, Northern residential (N75%) and filling station traffic through slip lane LOS A, queue on slip road (western approach) 19 metres Mall Rd Slip Rd

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