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Darren Blasdale - Seaford roundabout
- 1. Seaford Roundabout Presented by Darren Blasdale
- 5. TOTAL NORTH BOUND TOTAL SOUTH BOUND TOTAL EAST BOUND TOTAL WEST BOUND SEAFORDROAD (WEST) SEAFORDROAD (EAST) Green Shaded Dedicated crossing points Salmon Shaded Within 50m of the roundabout 27 1 1 57 0 0 62 33 41 PEDESTRAIN MOVEMENTS 3 7 17 12 13 20 42 GRAND BOULEVARD NORTH 29 19 0 2 GRAND BOULEVARD SOUTH
- 6. Delays 1min 37 sec 8:39am 2min 59 sec 3:26pm 11 sec 5:50pm 29 sec 8:51am
- 9. Crashes – • Engaged GTA consultants to investigate crashes and identify solution. • Based on casualty crash numbers over a 5 year period the intersection was eligible to be nominated for Black Spot funding. High entry speeds – • GTA to address vehicle speeds as part of the Black Spot nomination. • Investigate options to reduce vehicle speeds on the approach to the roundabout Delays– • GTA to undertake SIDRA modelling to capture existing traffic conditions and model proposed treatment to ensure LOS does not drop
- 11. Pedestrians still a concern– • Liaised with DPTI in regard to non-standard treatments. • Liaised with Jeremy Wooley from CASR in regard to adapting a safe system approach
- 23. Thank You
Editor's Notes
- Introduction Name – Traffic Engineer, City of Onkaparinga Subject So called title Seaford Roundabout!
- Location City of Onkaparinga Located over the hill
- Road functions Seaford Road is classified as a Distributor road providing connectivity between Seaford, Port Noarlunga and Moana to Main South Road and Southern expressway Grand Boulevard is a Collector road between Seaford Rise and Seaford Meadows
- Vehicle movements Seaford Road accommodates approx. 13,000 vehicle movements per day Grand Boulevard has approx. 5,000 vpd with a high number turning onto Seaford Road (east to travel to MSR) 1,300 right turns from south and 1,600 from north to Seaford Road east Issues Complaints over a number of years Speeding vehicles cutting lanes Poor sight lines on northeast corner Retirement village and school to the south – crossing 4 lanes of traffic Doctors surgery, Dr Jones and residential north of the roundabout Roundabout are good to reduce injury crashes not ped friendly
- Pedestrian Movements HDS to undertake a 12 hour traffic survey Total of 193 crossing movements Main crossing movements between north and south 71 between the doctors and retirement village 48 between schools and residential Not high compared to a lot of high pedestrian locations but has large number of vulnerable uses
- Current queue lengths and delays Worst case scenarios Southern leg Grand Boulevard related to school pick and drop off between 3pm for about 15mins accommodating 320 vehicles per hour
- Crash history DPTI crash map Total 13 crashes over a 5 year period 2012-2016 inclusive 8 resulting in injury Rear end hitting stationary vehicle and angled crashes
- Concerns Vulnerable pedestrians elderly and children crossing Seaford Road Number of crashes 13 over five years High entry speeds cars often cut between the lanes to maintain high speeds upto 50km/h Delays though not an issue generally worth capturing to ensure they are not extended over a longer period
- Investigations and solutions Crashes – We engaged GTA consultants to review the crashes particularly right angle crashes, improve sight lines and reduce entry and departure speeds.
- Create a concept design Bring forward the give way lines to improve sight lines Dedicated right turn lanes Extend centre median Required to accommodate 19m semi and buses Provide single exit lanes and through lanes to Seaford Road LOS hardly changed No pedestrian related crashes Submitted for federal Black Spot funding
- Agreed to install wombats on all approaches to create consistent approach and exit speeds on all legs DPTI agreed to wombats within 60km/h road Adapting safe system approach
- Originally had 2 Wombats but Jeremy suggested all legs to get consistent speeds Extended the centre annulus approx 2m each side to made it an egg-about – Natural movement Banned right out movement from GP Axis Short right turn lanes to accommodate crossing – Modelling shows it works
- Offset crossings to prevent pedestrians cutting straight through and reduced traffic delays Provided width for 2 gophers to pass each other Install 40km/h speed limit speed limit within roundabout Keyed in islands with reseal Back to back kerb considered between lanes
- Original black spot estimate $70,000 for 100% funding. Detailed estimate with 4 wombat crossings $368,000 mainly lighting and stormwater Project wasn’t funded so will have to undertake a staged approach DPTI increased black spot funding to $105,000 Final cost $127k by sub contracting work out
- Reduced design to sit on concrete and rubble in fill to reduce costs Management wanted to use paint on the centre annulus to further reduce costs Flush cut through Wombats not installed but can be retrofitted at a later date
- Large catchment area Installed banners on all approaches Met with retirement village, doctors and adjacent residents Put information on web site
- More educate how it will work than consult – Already know the issues Held open day at Seaford shopping centre where we discussed the treatment and played a fly through video Online trolls all put there opinion forward, some had alternative suggestions which included demolishing the medical centre and retirement village Many didn’t want to be slowed down
- This fly through was created in house by one our designers Infraworks, 3D studio max and Civil 3D
- REVIEW Used Thermo-plastic line marking should last 5 years Cars cutting painted median Pedestrian number have increased slightly, Though not all use the crossing area, many following the desire lines Will be interesting to get the crash data though haven’t heard of any yet Appears to be operating well And that completes my presentation………..