An underground car park refers to a vehicular parking facility built beneath ground level, commonly constructed under urban squares, public parks, roadways, or within the basements of major developments. It serves as a vital solution to ease ground-level land scarcity in city centres and segregate vehicular traffic from pedestrians. Its primary objective is to offer centralised parking capacity without taking up prime surface land, whilst integrating seamlessly with MRT stations, commercial hubs, and office towers to boost urban transport efficiency.
| Classification Parameter | Category | Key Characteristics |
|---|---|---|
| Excavation Depth | Shallow-depth (Single-level) | Roof slab sits close to ground level, offering better natural lighting and ventilation at a lower construction cost |
| Deep-depth (Multi-level) | Excavated two or more levels downward to maximise vertical space, though civil works, ventilation, and smoke extraction costs are substantially higher | |
| Construction Method | Integrated type | Constructed concurrently with the superstructure above, sharing the same foundation and shear-wall structures |
| Standalone type | Constructed independently beneath public squares, green reserves, or roads, fully detached from any surface building | |
| Driveway Layout | Ramp access | Vehicles navigate between levels via spiral or straight ramps, driven manually by motorists |
| Mechanical type | Utilises car lifts, stackers, and lateral shifting platforms for vertical or horizontal transfer; parking and retrieval are fully automated |
Lighting and Signage Systems:
Underground car parks require 24/7 artificial illumination—driveway illuminance must not fall below 50 lux, parking bays must achieve at least 30 lux, with intensified illumination at entry/exit points and corners. Escape routes and emergency exits must feature battery-backed emergency luminaires delivering a minimum backup duration of 90 minutes during power outages. Driveway carriageway markings, parking bay lines, and directional arrows must be clearly painted on floors, alongside reflective hazard markers and height restriction gantries (standard clearance ranges from 2.0 to 2.2 metres) fitted on pillars, walls, and tight turns.
Ventilation and Smoke Extraction Systems:
Basement car parks must be fitted with mechanical ventilation systems, with air exchange rates determined by total parking capacity and traffic volume, typically designed for 5 to 6 air changes per hour (ACH). Smoke spill systems must integrate with the fire alarm system, triggering smoke extraction mode automatically during a fire whilst supplying positive-pressure air to stairwells and protected lobbies to prevent smoke ingress into escape paths.
Drainage and Flood Mitigation Facilities:
Floors must incorporate perimeter drainage scupper drains and sump pits hooked up to municipal stormwater mains, with a floor gradient of no less than 0.5% to ensure the rapid run-off of wash-down and firefighting water. Entry and exit portals must incorporate trench drains and flood barriers (minimum 300 mm in height) to keep surface flash floods at bay. Sump pits must house bilge pumps configured in a duty/standby pair with automated float level switches.
Fire Protection Facilities:
Underground car parks must be equipped with indoor fire wet/dry risers and hose reels (spaced no further than 30 metres apart), ABC dry powder portable extinguishers, mobile trolley units, and an automatic fire alarm installation (incorporating smoke detectors, heat detectors, and manual call points). Fire compartments are generally capped at 4,000 square metres (where an automatic fire sprinkler system is installed), with each compartment served by at least two independent fire exits.
EV Charging Zone Provisions:
Car parks provisioned with EV charging infrastructure must cluster dedicated EV bays on the Ground Floor (Level 1) or Basement 1, demarcated as independent fire compartments. Charging bays must be enclosed with fire-rated walls of at least a 2-hour rating and floor slabs of a 1.5-hour rating, with compartment sizes capped at 1,000 square metres and served by direct fire exits. EV chargers must feature built-in overcurrent protection, earth leakage protection, lightning surge arrestors, and dedicated earthing, alongside electrical fire monitoring modules within distribution boards.
Key Electrical Safety Precautions:
Sub-main power cables for basement EV chargers must run through rigid metal conduit (GI) or heavy-duty flame-retardant PVC conduit; makeshift wiring and looping are strictly prohibited. Each EV charging bay must be protected by a dedicated Residual Current Device (RCD) rated at no more than 30 mA tripping current and a trip time of under 0.1 second. Warning signage reading "No Smoking or Naked Flames" and "Danger: High Voltage" must be conspicuously displayed, complemented by heavy-duty fire blankets and dedicated dry sand buckets.
Being enclosed, subterranean spaces, the impact of thermal runaway originating from an electrified vehicle's traction battery pack is significantly magnified compared to open-air surface car parks:
Smoke Accumulation and Toxic Fumes: Highly toxic gases such as hydrogen fluoride and carbon monoxide vented during thermal runaway accumulate rapidly in the absence of natural cross-ventilation, reaching concentrations many times higher than outdoors. This poses a grave hazard to occupants and BOMBA rescue teams alike. The hot gases rise via stack effect, threatening to compromise primary escape routes.
Severe Firefighting Challenges: Heavy fire appliances cannot navigate the low clearance of basement car parks. Internal wet riser pressure and water flow rates frequently fall short of the massive continuous water delivery required to cool lithium-ion cells down (typically 5 to 8 tonnes of water per vehicle fire). Furthermore, contaminated firefighting run-off pooling on basement floors risks causing secondary short circuits, electrocution, and environmental contamination.
Elevated Re-ignition Risk: Without prolonged core cooling, battery cells can re-ignite within minutes, creating recurring hazards for emergency crews inside confined basements. Given the tight parking density in Malaysian developments, a single vehicle fire can rapidly ignite neighbouring vehicles through intense radiant heat, triggering a devastating chain reaction.
Dedicated Mitigation Strategies: Basements should incorporate thermal imaging cameras and AI video analytics for 24/7 continuous temperature tracking across all EV charging bays, sounding audiovisual alarms upon detecting abnormal heat signatures. Dedicated sprinkler arrays and flammable gas sniffers positioned over charging bays enable swift automatic suppression during the incipient phase. Forward-thinking developments also specify drenching water curtains around EV zones to effectively contain radiant heat transfer.
Height Clearance Monitoring: Height limit gantries and high-visibility warning signs must be installed at entry ramps to prevent over-height lorries and vans from damaging overhead piping, conduits, and cable trays.
Housekeeping and Upkeep: Oil spills and ponding water must be degreased and mopped up immediately to prevent vehicle skidding; roadside drains, scuppers, and sump pits require monthly desilting to ensure unhindered discharge during downpours.
M&E Servicing: Mechanical ventilation blowers, sump pumps, and active fire installations require monthly preventative maintenance, alongside quarterly simulated fire alarm trip tests to ensure systems respond seamlessly on demand.
Standard Operating Procedures (SOP): Building management must establish and routinely drill targeted emergency response procedures covering structure fires, flash flood mitigation, EV battery smoking incidents, and tenant evacuation, ensuring all security and operational staff are well-versed in evacuation paths and outdoor assembly points.
Smart Parking Guidance and Car-Finding Tech: Overhead bay sensors and wireless geomagnetic detectors log bay occupancy in real time, relaying available bay counts via digital signboards and mobile apps; 'Find My Car' kiosk systems allow motorists to pinpoint their parked vehicles across sprawling multi-basement developments.
Automated Valet Parking (AVP) : Designed for Level 4 autonomous vehicles, drivers can alight at designated drop-off points while the car navigates ramps and parks itself autonomously into a bay. When leaving, the vehicle is summoned via smartphone to return to the pick-up lounge, dramatically boosting bay turnover and driver convenience.
Green Lighting and Energy Efficiency: Motion-activated smart LED fittings dim down during quiet off-peak hours whilst maintaining baseline safety lighting, turning up to full brightness only when vehicular or foot traffic is detected, thereby cutting landlord energy overheads.
Solar PV and Battery Energy Storage Systems (BESS): Standalone underground car parks increasingly feature rooftop solar PV arrays to supply clean electricity directly to EV fast chargers and common lighting circuits; paired with on-site BESS, energy can be peak-shaved and stored during off-peak hours for discharge during daytime tariff spikes.
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