RIGHT TURN MOVEMENT ACCESSIBILITY AT SILWOOD /LOUIS BOTHA Existing Situation at Silwood/Louis Botha

Technical Memorandum

RIGHT TURN MOVEMENT ACCESSIBILITY AT SILWOOD /LOUIS BOTHA Existing Situation at Silwood/Louis Botha

The right turning movement volumes at the gap in the median at Louis Botha and Silwood during the peak hours (AM and PM) is very low, especially when compared to Corlett Drive and Grenville/Newick intersections, as this has to be undertaken under priority/give way conditions. This is the same at Berkswell Road.

It should also be noted that currently when vehicles are performing the right turn manoeuvre, be it from the north or the south, that they are in fact blocking one of the through lanes along Louis Botha Avenue whilst waiting for a gap in the opposing traffic.

Future situation at Silwood/Louis Botha with BRT

The City of Johannesburg needs to prioritise Public Transport and especially for Rea Vaya Phase1C. Active steps have to be taken in the provision of infrastructure which gives the BRT priority over the private vehicle. For Phase 1C in particular we as JDA’s consultants were tasked to consciously promote the BRT and significantly increase its operating speed over the earlier BRT phases. This can only be done effectively by reducing the number of right turn phases across the path of the BRT.

Nevertheless some concession had to be made to still provide some right turn access at selected key intersections (major east –west routes) in order to still facilitate some access to the suburbs and neighbourhoods. A policy was adopted, which was approved by the City, that such right turn access would be provided at approximately 1 km intervals, with safe pedestrian signalised crossing opportunities provided at approximately 500m intervals along Louis Botha Avenue.

This principle was applied and the corridor traffic modelled so that an acceptable BRT bus operating speed could be achieved. The City then approved the proposed limited access scheme, since the bus speeds so achieved, were considered acceptable. When implementing a BRT system, the only way that a right turn can be provided at an intersection is if an exclusive right turn lane of significant length can physically be accommodated. The SA Traffic regulations also require that any signal phase for the right turning vehicles which will be located on the left hand side of the BRT lane, must operate under protected right turn signal conditions. This means that right turning vehicles may only proceed from the stopline when the green right turn arrow is displayed (as they will have a red signal displayed at any other time), and that no vehicles may store in the intersection, since these will be directly in the path of the BRT bus in the next signal phase. A further consequence is that no gaps in the median can be left when the BRT bus lane operates since a legal right turn across the BRT can only happen at designated signalized intersections.



The BRT operations plan makes provision for a BRT station to be placed to the south of Corlett Drive (Yellow DOT). The passenger access to the station is provided at the southern pedestrian crossing of the Corlett Drive intersection. The present width of Louis Botha Avenue at this section between Silwood and Newick/Grenville actually makes it impossible to provide any right turn bays at Silwood, even if an intersection were allowed. The road layout shown below illustrates why the intersection at Silwood and Berkswell cannot accommodate traffic across the BRT median. The forecast of 2018 BRT bus volumes during the peak hour is 171 buses per hour, or a bus every 20 seconds, reinforcing the need for an exclusive BRT lane and median, which is very unsafe to cross.





Deviation routes that need to be followed for right turns at Silwood

  1. North Bound Right Turn Option 1: Right turn on Newick, Left on Berkswell, Right on Howard, Left on Silwood
  2. North Bound Right Turn Option 2: Left on Silwood, Right on High, Right on Corlett, Right on Louis Botha, Left on Silwood
  3. North Bound Right Turn Option 3: Right on Corlett, Right on 1st, Right on Silwood
  4. South Bound Right Turn Option 1: Right on Corlett, Left on High, Left on Silwood
  5. East Bound Right Turn Option 1: West on Silwood, Left on High, Left on Grenville, Right on Louis Botha
  6. West Bound Right Turn Option 1: East on Silwood, Left on 1st, Left on Corlett, Right on Louis Botha

Conclusions

The City’s decision to give priority to public transport and in particular Phase1C of the BRT, means that it has approved the BRT implementation Plan of right turn access across the BRT only at approximately 1km intervals. It has further approved the consequent increase in BRT bus travel speed in order to reduce the bus turnaround time and consequent reduction in fleet size commensurate with this principle.

As a consequence, and because of the unique traffic conditions along the BRT corridor, it is NOT possible to provide priority controlled breaks in the median as currently. This is mainly for safety reasons, but also to comply with the SA Road Traffic act. It is also not safe to allow pedestrians across the BRT corridor except at signalized intersections.

Unfortunately therefore the route deviations described and shown above need to be followed in order to reach their destination by previously allowed right turn manoeuvres at the intersection of Louis Botha Avenue and Silwood Road.