An intersection reaches capacity when
queues grow at a greater rate than
traffic clearing the intersection.
Capacity is reached 3 times a day,
for a third of the working day.
Queues during holiday peak times are often more than 10km long.
Traffic will double in 10 years so
a sustainable re-design now is a priority.
5 intersections. 5 peak periods. 5km+ queues. 5% worse per annum. 5+years until anything is done.
The Hill Street intersection connects to two major arterials (Sandspit and Matakana Roads), which serves a growing population.
The crossing for pedestrians across Sandspit Road is not safe for the predominantly elderly who use it.
Waiting in congestion is a familiar experience for ambulance crews whose base is located close to the Hill Street intersection.
The recently annouced trial of restrictions into Elizabeth Street are a temporary fix for a wider design problem.
Here is a map showing the proposed roading and zoning for Warkworth. Please click on the map to enlarge.
There are four different green light phases. The sequences of the phases are based on data collected from sensors. With 10-20 second phases, an average of 1 vehicle per second can get through each phase, meaning that the traffic light part of the intersection has a capacity of 3,600 traffic movements per hour. When there is gridlock on Sandspit Road, the capacity is much lower.
Here is typical Sandspit Road and Elizabeth Street afternoon traffic.
A demonstration of 'Ghost Congestion', where congestion is caused by inexplicable hesitation.
Here is a queue of three truck and trailer units delivering metal to a subdivision construction site in Snells Beach. There are 13 other subdivision sites east of Warkworth whose construction traffic use the intersection with Hill Street.
Here is a traffic congestion map showing gridlock at the SH1/Hill St intersection at the end of a statutory holiday period. The queues stretch for 15+km on SH1, Matakana and Sandspit Roads.
Please click on image to have a closer look.
Of the four sets of traffic lights in Warkworth, Hill Street is a hub serving more than one connecting road.
The above diagrams show NZTA and AT traffic data and projections showing the growth of traffic at the intersection, even after the completion of the Tollway, Western Collector, and Matakana Link.
The above diagrams show NZTA and AT traffic evidence showing the growth of traffic at the intersection, even after the completion of the Tollway, Western Collector, and Matakana Link.
The above timelapse animation shows in two half hour periods how traffic congestion accumulates at the intersection using the current intersection configuration.
Here is the graphic released by Auckland Transport announcing the proposed trial to restrict State Highway 1 and Hill Street into Elizabeth Street.
The State Highway 1 intersection with Hill Street at Warkworth is a perfect storm that is going to get worse. The problem was identiifed in the 1970s yet nothing has been done to fix some very obvious design flaws.
Here is a list of the design and traffic issues which combine to cause gridlock and frustration:
There are long delays;
Restrictions have exacerbated the problem;
Heavy construction traffic for nearby road works will cause congestion/gridlock.
Emergency Services aim to attend to scenes and recover injured to hospital within a "Golden Hour." Due to the congestion, instead of using ambulances located within 500 metres of the intersection, a rescue helicopter flies 50km from the Auckland Heliport in downtown Auckland.
The intersection was first surveyed in 1924 and has changed little since. In 1954, Browns Road (the current State Highway 1 route to the south of the intersection) was built. In 1971, Millstream Place was built. Traffic lights were added in 1996.
Below is a gallery of the intersection over the years.
Please scroll down to read about each issue in more detail.
LIVE TRAFFIC UPDATES
Waiting is not an acceptable option for emergency services.
There are three safety issues with the State Highway 1 intersection at Hill Street:
That emergency services are often stuck in congestion at the intersection;
That pedestrian and cycle crossings are dangerous; and
That entering and exiting Elizabeth Street and Kowhai Park is perilous.
Whilst the cause of the congestion issue is explained further down this page, the fact that emergency services find themselves delayed when responding to emergencies throughout the region increases the severity of the problem and should ensure that minimising congestion is a priority.
The NZTA usually prioritises safety issues above congestion and journey times. We say that when congestion increases the journey times for emergencies then it is a safety issue.
The majority of emergencies responded to by Warkworth-based emergency services have been to the north of Warkworth, meaning that police, ambulances, and firecrews have needed to negotiate the Hill Street intersection. In the past year, we have counted thirteen serious car crashes during peak traffic where emergency services have been delayed by congestion at the intersection.
Pedestrians who live in the suburbs north of the Hill Street intersection do not have a safe crossing of Sandspit Road. The crossing isn't marked on the road or signposted. A major arterial with many intersections in close proximity also reduces the awareness of pedestrians to motorists. Considering school pupils and elderly frequent this crossing, it is fortunate that there haven't been any major incidents.
Auckland Transport has, however, recently announced one short term safety improvement that it plans to trial from December 2016. As shown in the diagram to the right, they plan to restrict State Highway 1 and Hill Street traffic from entering Elizabeth Street. This will reduce traffic at that intersection and make it safer from Elizabeth Street traffic to make right turns.
The safety improvements are, in fact, impediments. A longer term solution should address the overall design of the intersection so that traffic isn't limited in their choices of route to take.
An intersection reaches capacity when
queues grow at a greater rate than
traffic clearing the intersection.
Major Regional Hub
The State Highway 1 intersection at Hill Street is one of four sets of traffic lights through Warkworth. The traffic light contollers at Hudson Road (to the north) and Whitaker Road (to the south) sends waves of traffic towards the intersection with Hill Street.
The road network at Warkworth and its hinterland depends on a 'hub and spoke' format where many arterial roads converge at a central intersection. Sandspit and Matakana Roads are arterial roads with few roads providing alternative routes.
Local roads also provide few practical alternative routes. Hill Street, which has a school and sportsfeilds, has Hudson Road and the Falls Road/Woodcocks Road. Even the Mansel Drive connector between Falls Road and Woodcocks Road is a 1200m detour.
Area of Growth
By the time that the extended Tollway bypasses Warkworth, local traffic at the intersection would have grown by more than what then uses the tollway.
When the current route for State Highway 1 along Browns Road was completed in the 1954, it wasn't long before congestion at the Hill Street intersection became a problem. Since the 1970s, there have been numerous complaints, numerous proposals, and no solutions.
Meanwhile, the traffic has increased and so has the congestion. More recent 'solutions' will only make matters worse.
Politicians have repeatedly argued that the Puhoi-Wellsford Northern Motorway/Tollway 'Road of National Significance' will 'solve' congestion at intersections through Warkworth. The problem with this argument is fivefold:
A significant proportion of traffic using the proposed tollway will turn right towards Warkworth and use the Hill Street intersection;
Before the completion of the tollway, the local traffic using the intersection will grow by more than the traffic expected to use the new tollway;
The NZTA has set aside a budget of $20million - $100million to 'improve Warworth intersections', but will instread divert the funds towards new roads that exacerbates the existing intersection problems;
The Auckland Council, thinking that proposed roads will fix the problem, have proposed extending the Warkworth urban boundary north of the intersection, which will allow for a further 1900-2200 dwellings; and
The construction traffic for other projects will cause more congestion at the Hill Street intersection than any potential improvements to the Hill Street intersection.
In the above map, the blue dotted line shows the route of the proposed extension of the Northern Tollway from Puhoi. The green dotted lines show the suggested route of collector roads between the arterial roads and the state highway.
A state highway is a limited access road where development is controlled by the NZTA, who administer the planning of the highway network, and local authorities, who adminster the district plan. The reason why development is restricted along such roads is that the more intense the development is along a road, the more accessways to the road, the more traffic, and the more likely that the flow of traffic will be disrupted.
A busy road is attractive to commercial activities and convenient to residential activity. The term 'ribbon development' is when development relies on a single road without providing their own connecting local or collector roads. Such development where many accessways are clustered together can result in traffic disruption that requires the lowering of speed limits to 70km/h and 50km/h to maintain safety.
The proposed collector roads around Warkworth can not be considered 'solutions' to congestion at Hill Street. Instead of just distributing traffic from a point at one end of the town to the other, the collector roads will collect traffic along the way.
The collector roads will collect traffic and slow down through traffic. The Auckland Unitary Plan proposes extending the Warkworth urban boundary which will allow for 3700-4300 new dwellings in the Southern Growth Cell flanking the Western Collector Road and the Northern Growth Cell flanking the Matakana Link Road could contain 1900-2200 dwellings.
When the NZTA prepared its case for the tollway extension, they prepared evidence to the Board of Inquiry considering its resource consent application. This evidence included traffic projections of the effect of the motorway on traffic through Warkworth.
In the diagrams to the right, we have collated that evidence. We have taken into account historical data, NZTA's historical projections, and compared that with their subsequent projection adjustments.
In a nutshell, traffic growth has been greater than what NZTA 'guessed' and will be greater than what they suggest. Using NZTA's own evidence, the proposed motorway, Western Collector, and Matakana Link Roads will increase traffic congestion at the State Highway 1 intersection with Hill Street.
NZTA would better serve the taxpayer by focusing its resources on the root of the problem rather than avoiding it.
To demonstrate the severity of the 'do nothing' option, we have taken the NZTA's traffic data, got hold of the traffic modelling software that the NZTA use, and created simulations of the traffic.
In the video below is our simulation of peak traffic at the beginning and end of statutory holidays in 2009 and 2026. This video shows traffic building from a base of zero to peak flow in two 15 minute periods. Even after 15 minutes, the queues are 500m long!
Too many intersections
Linking all these local and arterial roads with the country's main state highway has produced five intersections within 100 metres. Check out the map to the right, which shows all the intersections and give way signs.
Intersections that can't be described on a road sign are dangerous. It is confusing that Sandspit Road starts at the junction with State Highway 1 but motorists need to turn right within 100 metres across Matakana Road traffic to continue along Sandspit Road.
Just count the number of decision points. It is no wonder drivers are confused and struggle to decide when it is safe to enter the intersection.
For the majority of the time, northbound traffic
turns right at three of the intersections,
needing to give way to all other traffic.
State Highway 1 effectively bisects Warkworth. The majority of the local traffic crosses from one side of the state highway to the other.
At the intersection with Hill Street, the majority of northbound traffic turns right towards Matakana and Sandspit, crossing southbound State Highway 1 traffic. Sandspit traffic also has to give way to southbound Matakana Road traffic.
In a nutshell, when one stream of traffic wants to turn right, someone has to give way. The issue is: who should give way?
Unless the intersection is signalised, the right turn relies on gaps in the traffic. More traffic means less gaps and eventually no gaps. The only solution in such a scenario is traffic signals or underpasses/overpasses.
The tollway and proposed collector roads do not address this problem. Instead, the junction for the tollway with State Highway 1 will be a roundabout where the majority of southbound traffic will turn right towards the tollway and the majority of tollway traffic will turn right towards Warkworth, resulting in the same congestion dilemma as what occurs at the intersection at Hill Street.
The suggested Matakana Link Road is no different. At the junction between the proposed road with Matakana Road, the proposed road traffic will yield to the predominant local traffic along Matakana Road.
Any suggested road design needs to improve the ability of traffic crossing the state highway without disrupting state highway traffic flow.
Every time someone turns right,
someone turning left has to give way.
There isn't sufficient space to queue,
causing gridlock for everyone else.
Five intersections within a 100 metre diameter serving eight connections already provides an array of turning combinations. This is further confused by seven left-turning lanes and two merging lanes.
Ironically, these turning areas were to simplify the intersection. What they do instead is create another t-shaped intersection close to another intersection.
Take, for instance, the left-turning lane from southbound State Highway 1 traffic. That traffic can not only turn left but also head straight towards Elizabeth Street. At the same time, not knowing what the traffic lights signal, the traffic must also give way to any traffic from Hill Street and northbound State Highway 1. The left-turning traffic isn't necessarily looking straight ahead at possible hazards from Kowhai Park, Sandspit Road, or Elizabeth Street.
The right-turning merge lane from Millstream Place and left-turning lane into Sandspit Road are the same space.
Any intersection should be predictable for all traffic. Being able to predict other traffic is a key component to achieve this.
Northbound Elizabeth Street traffic turning in any direction needs to take into account traffic from four directions.
Sir Isaac Newton stated that every action has an opposite and equal reaction. In the case of the merging traffic at the intersections, other traffic has to react to it.
With each of the eight connecting roads having seven routes, there are 55 turning combinations at the intersection (taking into account that there is a no right turn into Hill Street). Of these 55 turns:
11 are controlled by traffic lights;
5 have to give way to one direction;
22 have to give way to two directions;
12 have to give way to three directions; and
5 have to give way to four directions.
One driver's hesitation generates precaution in other drivers, which can trigger a chain reaction. Stopping and starting, acceleration and deceleration causes delay, queues, and congestion.
Any design for an intersection needs to simplify the navigation for users.
Traffic Light Delays
Traffic light controllers sense traffic and then
factor that information into a sequence.
Often, there is a delay in the sequencing programming that causes delay for motorists.
Traffic lights control traffic at intersections where the flow of connecting roads are so significant that conventional signage is insufficient to avoid congestion. Traffic lights sequences are based on various inputs such as fixed programmes or dynamic algorithms based on information collected from sensors near the intersection.
Traffic lights are designed to stop some traffic to allow other traffic through, creating gaps in traffic. While Hudson Road and Whitaker Road traffic lights provide gaps, the stop and starting creates waves of traffic that can cause congestion.
The problem with traffic lights is that the red light period is longer than the green light period. During a red light, traffic queues build up. If each green light period does not allow the queue to reduce, the intersection has reached capacity and congestion results.
At the intersection with Hill Street, capacity is reached many times a day. At the root of the problem is that:
For every second of green light, there might be 3 seconds of red light;
Each green light might allow 10-20 vehicles through;
Because traffic can wait 3 times longer than the green light period, even a flow of 5 vehicles wanting to get through the intersection could generate a queue of 20 vehicles; and
As the flow increases above 5 vehicles, the queues accumulate rapidly.
For Sandspit Road, the sensors do not necessarily provide accurate data to the traffic controllers. The queue between State Highway 1 and Elizabeth Street can only measure a maximum queue of 3 vehicles. Between Elizabeth Street and Millstream Place, a maximum of 5 vehicles can queue.
To maximise capacity, every approaching lane will need two lanes long enough to store all vehicles delayed by the signals.
We know that the traffic light sequences are a major concern of many locals. We know the traffic controllers watch the social media pages and Warkworth Traffic updates. Community feedback on these sites has helped manage the traffic lights over the last summer period.
We know, however, that traffic lights alone are not the solution to improving traffic flow at the intersection with Hill Street. The whole configuration of the intersection needs to be taken into account.
The intersections reach their capacity three times a day.
As right turning lanes are short, through traffic in both directions often have to wait for turning traffic to clear.
The queuing problems at the intersection with Hill Street is not just their length and frequency. The most frequent problem is how they form.
There are two different types of queuing:
Queues caused by red lights; and
Queues caused by through traffic stuck behind queues for turning traffic.
Within the first 100 metres of Sandspit Road from the intersection with State Highway 1, there are three areas that must be kept clear of traffic to avoid obstruction of intersection traffic.
Clearways influence traffic movements as, for each vehicle moving forward, there must be a space available. The leapfrogging complicates traffic flow.
For heavy vehicles, the problem is worse. The queuing space between State Highway 1 and Elizabeth Street is insufficient for longer vehicles, often resulting in trailers blocking traffic in and out of Elizabeth Street. It only takes one truck/trailer unit to block the intersection.
The cause of the longest queues is due to through traffic stuck behind turning traffic. The dedicated turning lanes in both directions along State Highway 1 are not long enough for queuing turning traffic.
To the right is a video clip demonstration of what is called 'Ghost Congestion', where hesitation can cause a chain reaction, which causes queues and congestion. Such behaviour is a regular occurance at the Hill Street intersection at many points.
According to official statistics, the intersection with Hill Street is a low crash area - mostly due to the congestion and confusing format. In other words, traffic is too cautious or traveling too slow to be considered dangerous.
The most dangerous element of the queuing is that emergency services struggle to get through the intersections. Rescue helicopters are often deployed instead of ambulances. Police and the fire service responding to emergencies, such as crashes at Dome Valley (a notorious black spot), are delayed.
While many other 'dangerous' intersections thoughout the country have been 'upgraded', Hill Street has been overlooked. Even scheduled works were suspended in the misguided belief that other projects would 'fix' the problem.
Whilst NZTA has already allocated a budget to improve Warkworth intersections, Hill Street can not be overlooked any longer. We are sick of waiting.
Restricting right turns to Elizabeth Street will just send traffic on a long detour through other congested intersections,
including the Hill Street intersection.
One attempt by the NZTA to reduce waiting times at the intersection with Hill Street has been to reduce the number of turn combinations in the traffic controller cycle.
The first 'trial' was to restrict the least chosen turning combination - the right-turning traffic from southbound State Highway 1 into Hill Street. The rationale is that by stopping turns across northbound State Highway 1 traffic would allow longer green light periods for northbound State Highway 1 traffic.
Northbound State Highway 1 almost halves at the intersection with Hill Street. In other words, half of the traffic turns right into Sandspit Road. The queues that form at the intersection for northbound traffic is mostly due to right-turning traffic queues blocking through traffic, not through traffic queues blocking right-turning traffic.
Technically speaking, right-turning traffic into Sandspit Road should not conflict with right-turning traffic into Hill Street. Sensors can detect queues of 5 vehicles wanting to turn right into Hill Street and allow 5 second green light periods to let that traffic through when northbound through traffic can allow.
Instead, for the sake of 5-10 extra seconds of green light for northbound through traffic, traffic wanting to enter Hill Street (often school traffic) has to turn right at the Hudson Road traffic lights 1 kilometre to the north and head through an industrial estate on an almost 2 kilometre detour.
So, in other words, as the traffic light sequence at Hudson Road has been changed to accommodate the extra right-turning traffic (and signage erected to inform motorists of the changes), the minor problem at one point has been moved elsewhere are a major inconvenience to those affected.
Making such changes has another consequence. Turning decisions of motorists must be made ahead of the logical point.
The 'trial' is now permanent. The next 'trial' is to restrict traffic into and out of Elizabeth Street.
During Northern Motorway extension construction,
50 heavy vehicles will use the intersection
8 times a day - struggling to negotiate it.
A considerable component of the growth in traffic at the intersection with Hill Street has been commercial and heavy vehicles transporting labour, equipment and materials to construction sites at new subdivisions and developments in Omaha, Point Wells, Matakana, and Snells Beach. Over the next decade, construction traffic will increase due to the following:
Construction of the Northern Motorway/Tollway extension from Puhio;
Construction of the Western Collector and Matakana Link Roads; and
Construction of infrastructure and housing in the Northern and Southern Growth Cells in Warkworth.
There are contractor yards and quarries on Matakana Road. It is estimated that as many as 50 trucks and trailors will make 3 return trips from quarries to the construction site, all using the intersection with Hill Street. That's 300+ traffic movements each work day.
According to the conditions of consent for the Northern Motorway extension, construction traffic can only operate for four hours of the day. This effectively doubles the construction traffic during those four hours of the working day.
Heavy vehicles already struggle to negotiate the queues and turns of the intersection. Taking into account the traffic light cycles, the considerable increase in heavy vehicle traffic will reduce the amount of other traffic able to get through each green light to virtually nill, i.e. gridlock.
The NZTA, however, have stopped any improvements to the intersection at Hill Street until the Northern Motorway extension and other collector roads are completed.
Effectively, what this means is that a lot of roads will be built elsewhere to bypass the Hill Street intersection, not spending a cent to fix Hill Street until those roads are built, but in the meantime clog up Hill Street intersection with construction traffic to build those new roads.
We say, spend the money on Hill Street intersection now before congestion gets any worse... And it will get worse.
Here is part of the original survey of the northern end of Warkworth, 1924.