Aanpak Ring Zuid Groningen Live Cam

Planning and Early Proposals

The concept of a southern ring road for Groningen dates back to the late 1960s, when urban planners identified the need to divert through‐traffic away from the historic city center. Initial proposals called for a circumferential route connecting the A7 motorway at Waterhuizen to the A28 near Zuidlaren, forming a half‐circle around the densely populated southern districts. By 1972, a regional transportation study recommended constructing a “Ring Zuid” that would link Hoendiep, Radesingel, and the Van Starkenborghkanaal crossings, thereby relieving pressure on the Ooster‐Noord‐Zuid axis (hereafter referred to as ONZ Axis).

Early design concepts envisaged predominantly surface‐level carriageways, utilizing asphalt concrete pavement over compacted subgrade. Soil borings at 50‐meter intervals revealed heterogenous peat layers—varying from 1 to 4 meters in thickness—overlying glacial clay and sand deposits. Geotechnical engineers recommended deep dynamic compaction in sections where peat thickness exceeded 2.5 meters, to achieve a minimum CBR (California Bearing Ratio) of 3 percent. In areas where compaction proved insufficient, preloading with surcharge fill of 1.2 meters was used to induce primary consolidation before final pavement construction. These soil stabilization measures would later prove essential for mitigating settlement exacerbated by Groningen’s ongoing gas extraction activities.

1960s Vision and Community Response

During the mid‐1970s, the Municipality of Groningen held a series of public hearings to gauge local residents’ sentiments regarding the proposed route. Neighborhood associations from De Wijert and Herewegbuurt voiced concerns about increased noise pollution and potential severance of residential areas. As a compromise, urban planners proposed constructing the Korrewegwijk Tunnel—a cut‐and‐cover structure beneath the Hereweg intersection—to maintain street connectivity while allowing through‐traffic to pass unobstructed. Acoustic engineers suggested installing 2.5‐meter‐high noise barriers made from sound‐absorptive concrete along residential parcels adjacent to the future ring road.

At the same time, environmentalists campaigned to preserve the peat meadowlands along the Hoendiep corridor. As a concession, the final design incorporated two wildlife underpasses—each measuring 3 meters in width and 2.2 meters in height—constructed using reinforced concrete box culverts, enabling small mammals and amphibians to cross beneath the roadway without risking collision. Culvert entrances were landscaped with native reed beds and sand lizards’ basking areas, reflecting an early commitment to ecological mitigation.

Design and Soil Challenges

By the early 1980s, technical drawings specified a dual carriageway with a total width of 24 meters, including two 3.5‐meter traffic lanes per direction, a 1‐meter central reservation, and 2.5‐meter hard shoulders on each side. The pavement cross‐section comprised the following layers (from top to bottom):

• 4 cm SMA‐C (Stone Mastic Asphalt, 10 mm nominal aggregate, polymer‐modified binder)
• 8 cm AC‐W (Asphalt Concrete, 16 mm nominal aggregate)
• 25 cm GAB (Graded Aggregated Base, crushed basalt with 0/32 mm grading)
• 15 cm subbase of stabilized sand–cement (4 percent cement by weight)
• Compacted subgrade (target CBR ≥ 4 percent after stabilization)

Subsurface drainage trenches, located 1 meter below the GAB layer, ran longitudinally along both edges of the roadway. These trenches consisted of perforated PVC pipes (diameter 160 mm) encased in a 30 cm thick gravel envelope (10/14 mm crushed stone), backfilled with free‐draining sand to quickly channel water away from the pavement structure. At regular intervals of 100 meters, vertical inspection shafts allowed maintenance crews to remove silt and inspect perforations, ensuring long‐term efficiency of the subsurface drainage system.

Construction Phases and Major Structures

Korrewegwijk Tunnel

Construction of the Korrewegwijk Tunnel began in 1984, using a cut‐and‐cover method. Initially, the municipal geotechnical team installed 120 soil nails—each 4 meters long with 38 mm diameter, grouted into the surrounding fill—to support the temporary excavation cofferdam. The excavation box measured 20 meters in length, 15 meters in width, and 6 meters in depth. Once the excavation was complete, prefabricated reinforced concrete deck slabs—each 6 meters wide by 3 meters long and 25 centimeters thick—were placed on top of reinforced walls built from CEM III‐A concrete with a 28‐day compressive strength of 50 MPa. The tunnel’s interior height was designed at 4.5 meters to accommodate emergency vehicle clearance and ventilation ducts.

To mitigate settlement effects, engineers installed 110 raked sheet piles (AZ 20‐700 profiles) along the tunnel’s periphery, driven to a depth of 15 meters to penetrate dense sand strata. On top of the sheet piles, a 0.6‐meter‐thick reinforced concrete plinth ring distributed lateral earth pressures uniformly. A permanent ventilation system, including axial fans rated at 15,000 m³/hour, was integrated to maintain air quality, removing vehicle exhaust composed of CO, NOₓ, and particulate matter. LED lighting fixtures—each consuming 45 W and achieving illuminance levels of 100 lux on the driving surface—were spaced at 5‐meter intervals to ensure uniform visibility throughout the 200‐meter length of the tunnel.

Hoendiep Crossing and Viaducts

The southern section of the ring required crossing the Hoendiep canal. Construction of the Hoendiep Viaduct occurred between 1986 and 1988. A 350‐meter‐long prestressed concrete bridge with seven spans was designed to minimize interference with canal navigation. Each span measured 50 meters, supported by cast‐in‐place piers founded on 12 precast concrete piles—each pile 0.6 meters in diameter and driven 18 meters into a dense sand layer to achieve tip bearing in glaciofluvial deposits. The superstructure consisted of precast I‐girder segments, each 2 meters deep, post‐tensioned longitudinally with 15‐strand 15.7 mm diameter tendons (greased and sheathed in HDPE ducts). Concrete grade C35/45 was specified for both girders and deck slabs, ensuring a 50‐year design life with minimal maintenance.

The bridge deck featured an inverted T‐shaped precast concrete barrier along each edge, 0.7 meters high, complying with NEN‐EN 1317 standards for impact performance. Expansion joints consisted of neoprene seals set into stainless steel frames, accommodating longitudinal movements up to ±20 mm due to thermal variations. Underneath the central span, navigational clearance was maintained at 4.2 meters above the water level, allowing passage of typical inland cargo vessels. Beneath the piers, scour protection consisted of 0.5‐meter‐thick riprap—rock fragments ranging from 150 to 300 mm—to prevent erosion caused by tidal currents in the Hoendiep.

Surface Roadway and Associated Structures

A key component of the Ring Zuid project involved constructing overpasses at major intersections to preserve uninterrupted traffic flow. At the intersection with the Verlengde Hereweg, a three‐span steel composite bridge was erected. Each steel plate girder—fabricated from grade S355 steel—measured 1.8 meters in depth and 0.6 meters in flange width, supporting a 30‐centimeter reinforced concrete deck slab. The total span over the Hereweg road measured 45 meters, with steel bearings accommodating ±75 mm of longitudinal expansion. Underneath, a reinforced concrete moat directed stormwater runoff from the interchange ramp into a settling basin equipped with a 1,200 mm diameter vortex flow control structure, reducing peak discharge into the municipal sewer system by 30 percent.

To accommodate pedestrian and cyclist traffic, a dedicated 4‐meter wide path was constructed parallel to the main carriageways. The path featured a 60 mm thick wearing course of epoxy‐bound gravel (16/8 mm) over a 150 mm base of mechanically stabilized earth (MSE) reinforced with geogrid layers. This pavement system was chosen for its high skid resistance (mu ≥ 0.6) and flexibility to accommodate minor settlements without cracking. Protective barriers—comprised of 1.2 meter high handrails with vertical balusters at 150 mm centers—separated cyclists from motorized traffic, ensuring safety in regions where horizontal clearance narrowed to 1.5 meters between edge of carriageway and adjacent retaining walls.

Surrounding Neighborhoods and Cultural Landmarks

Herewegbuurt and the University Medical Center Groningen (UMCG)

To the east of the Ring Zuid lies the Herewegbuurt, a neighborhood defined by early 20th‐century row houses and the prominent tower of Martinitoren visible on the horizon. The new ring road provided a bypass for traffic that would have previously tunneled through narrow residential streets near the UMCG campus. Today, sound barriers constructed from transparent polycarbonate panels, each 3 meters high and treated with an anti‐graffiti coating, screen noise from the medical complex, maintaining interior ambient levels below 55 dB(A) when roadway volumes exceed 25,000 vehicles per day.

Just south of the ring road exit ramp at Hoendiepstraat, the UMCG’s research laboratories sit atop a complex system of groundwater monitoring wells and piezometers. These instruments, installed during road construction, proved invaluable in tracking subsidence trends associated with Groningen’s gas extraction. Data from the piezometers—measuring hydraulic head at depths between 5 and 20 meters—helped adjust embankment compaction strategies to mitigate accelerated settlement that threatened utility conduits running beneath the road.

De Wijert and Oosterpoort Districts

West of the ring road, the De Wijert neighborhood features a combination of mid‐century apartment complexes and green spaces. During construction, soil improvement techniques—such as wick drains topped with temporary surcharges—expedited consolidation of soft clay layers beneath nearby parkland, preventing lateral spreading toward the adjacent playground. The Oosterpoort cultural complex, a former synagogue converted into a music venue, is accessible from the ring road via a short arterial road—Stadsweg—featuring a traffic signal system synchronized using SCOOT (Split Cycle Offset Optimization Technique) to minimize delay for concertgoers.

Traffic engineers implemented a roundabout at the intersection of Ring Zuid and Oosterhoogebrug, employing a 30‐meter central island with mountable curbs elevated 150 mm above carriageway level. The roundabout’s entry radii were set at 25 meters to accommodate 12‐meter long articulated buses, while the circulatory roadway width varied between 6 and 7 meters, ensuring smooth two‐lane circulation during peak hours. LED‐lit lane markings—using thermoplastic material with retroreflective glass beads—enhanced nighttime visibility, guiding drivers through the roundabout’s curved geometry.

Hoornsemeer and Peat Meadowlands

South of the Ring Zuid, the Hoornsemeer recreational area offers a contrast to the engineered roadway. This glacially formed lake—spanning 0.8 square kilometers—was integrated into the ring road’s design with carefully placed embankment transitions to avoid disrupting natural hydrology. To protect fish spawning grounds, aquatic biologists installed temporary silt curtains during culvert installations, preventing turbidity spikes in water depths ranging from 1 to 3 meters. The completed culverts—two parallel 1.5 meter by 1.2 meter reinforced concrete box structures—allow uninterrupted fish migration under the roadway, framed by riparian zones planted with native sedges and wetland grasses.

The adjacent peat meadowlands required specialized embankment construction. In one section, engineers employed prefabricated vertical drain bundles composed of geotextile-wrapped synthetic wick drains encased in gravel, accelerating the consolidation of underlying peat. This reduced long‐term settlement from an estimated 50 centimeters over 30 years to under 20 centimeters, ensuring the ring road’s surface remains within design tolerances. In areas where peat depth was under 1 meter, shallow strip footings of reinforced concrete—1.2 meters wide and 0.5 meters deep—supported lighting columns and noise barriers, eliminating the need for deep piling in less critical zones.

Modern Traffic Management and Future Upgrades

Intelligent Transport Systems (ITS)

Since 2010, the Ring Zuid has incorporated ITS features aimed at optimizing traffic flow. Variable Message Signs (VMS)—each equipped with LED matrices offering pixel resolutions of 128 × 64—are installed at strategic locations, including just before the Korrewegwijk Tunnel portal and near the Hoendiep exit. These signs display real‐time travel times, lane closure alerts, and congestion warnings. Roadside units equipped with microwave radar sensors measure vehicle speeds and classify vehicles into categories (cars, light trucks, heavy trucks) based on radar cross‐section profiles. Data is transmitted via a dedicated 5.8 GHz 802.11p network to the Traffic Control Center, where algorithms adjust signal timings on adjacent arterial roads to balance demand and reduce queuing.

In 2018, a pilot project introduced Bluetooth MAC address detection units at two locations—one at the southern approach to the Hoendiep Viaduct and another at the Korrewegwijk exit. These units anonymously track device presence to estimate journey times, providing data with an accuracy of ±5 percent. Aggregated data informs adaptive speed limit signs, which dynamically reduce posted speeds from 100 km/h to 80 km/h when average section speeds drop below 60 km/h, smoothing stop‐and‐go waves and reducing accident risk.

Impact of Gas Extraction and Subsidence Mitigation

The Groningen gas field, lying approximately 25 kilometers to the east, has induced measurable land subsidence across the region. Differential settlement rates of 3 to 5 millimeters per year were recorded along the Ring Zuid corridor between 2005 and 2015. To counteract this, structural engineers retrofitted certain sections of the dual carriageway with adjustable bearings where overpasses crossed canal locks. These bearings—Elastomeric pads measuring 500 mm by 500 mm—allow for vertical adjustments of ±50 mm, enabling maintenance crews to recalibrate deck elevations in response to cumulative subsidence. Pavement maintenance cycles were shortened to five years instead of seven, allowing resurfacing teams to address rutting and cracking exacerbated by episodic sinking.

At locations where subsidence threatened the gradient of drainage channels, hydrologic engineers installed adjustable weir plates in culverts to maintain a minimum 0.5 percent slope for effective stormwater conveyance. Failure to address these gradients could have led to standing water on the pavement after heavy rains—a hazardous condition in freezing temperatures common during February and March. Annual surveys using LiDAR-based mobile mapping vans precisely measure roadway elevations to within ±10 mm, guiding proactive rehabilitation measures before safety-critical thresholds are reached.

Tip: To gain a unique vantage of the Ring Zuid’s alignment and its integration into Groningen’s urban fabric, consider renting a bicycle and following the parallel cycle path westward from the Hoendiep Bridge toward De Wijert; along the way, notice how the noise barriers and lighting masts create a rhythmic visual corridor contrasting with the adjacent municipal parkland.

Interesting Fact: Beneath the reconstructed section north of the Korrewegwijk Tunnel lies an abandoned peat‐cutting canal dating to the early 17th century, rediscovered during subsurface utility trenching in 2002. Archaeologists found wooden sledges and clay pipestems within its silty bed—evidence that peat was once transported via small barges to fuel local bakeries in Groningen’s city center.