IRC 99:2018 is the Indian Standard (IRC) for tentative guidelines on the provision of speed breakers for control of vehicular speeds on minor roads. IRC 99:2018 specifies the design and application of speed breakers for traffic calming on Indian minor roads, urban streets, and sensitive areas. Speed breakers come in three forms: round-top humps (most common, 100 mm × 3.7 m parabolic, forces 20-25 kmph), flat-top raised tables (75-100 mm height, 3-5 m flat top, comfortable at 30-40 kmph), and rumble strips (25 mm × 300 mm, multiple strips for advance warning). Critically, IRC 99 explicitly PROHIBITS speed breakers on National Highways, State Highways, arterial roads, bus routes, and roads with gradient > 5% — these locations need different speed-management strategies. Amendment No. 1 (2021) added pre-formed rubber speed humps for temporary installations and smart speed breakers with illuminated markings for night visibility. Indian minor roads often have poorly-designed, unauthorized speed breakers — causing vehicle damage, passenger discomfort, and emergency vehicle delays. IRC 99 compliance requires proper authorization, design, signage, and maintenance. Speed breakers should be LAST RESORT for speed control; other measures (speed cameras, road narrowing, chicanes) often preferable.
Specifies design, location, and application of speed breakers (humps, rumble strips, raised tables) for traffic calming on minor roads, urban streets, school zones, hospital approaches, and accident-prone locations — NOT for major highways or arterials.
Key geometric dimensions, placement criteria, signage requirements, and material guidelines for rounded speed breakers on minor roads.
| Reference | Value | Clause |
|---|---|---|
| Recommended Profile Type— Trapezoidal/flat-topped humps are not recommended by this code. | Rounded (Hump) | Cl. 4.1 |
| Height of Speed Breaker (h)— This is the maximum recommended height for the specified profile. | 100 mm | Cl. 4.2.1 |
| Width of Speed Breaker (w)— Corresponds to a 17 m radius and 100 mm height. | 3.7 m | Cl. 4.2.1 |
| Radius of Speed Breaker (r)— For a design crossing speed of 25 kmph. | 17 m | Cl. 4.2.1 |
| Design Crossing Speed— The target speed for a vehicle crossing the breaker. | 25 kmph | Cl. 4.2.1 |
| Shape Formula (w, r, h)— Relates width (w), radius (r), and height (h) of the hump. | w = 2√(2rh - h²) | Cl. 4.2.1 |
| Length of Speed Breaker— To prevent vehicles from swerving to avoid it. | Full Carriageway Width | Cl. 4.2.2 |
| Code Applicability— Not for use on National Highways or State Highways. | Minor Roads | Cl. 1.1 |
| Preferred Location (Urban)— Where traffic is controlled by stop/give-way signs. | T-intersections of minor roads | Cl. 3.1.1 (i) |
| Preferred Location (Rural)— On minor roads with carriageway width ≤ 5.5 m. | Approaches to sharp curves | Cl. 3.1.2 (i) |
| Placement on Gradients— Avoid placement on steep gradients to prevent vehicle scraping. | Not Recommended | Cl. 3.2 (i) |
| Placement on Horizontal Curves— To avoid loss of control, especially on sharp curves. | Not Recommended | Cl. 3.2 (ii) |
| Spacing between Breakers (Series)— Depends on the desired speed between the humps. | 100 m - 120 m | Cl. 3.3 |
| Mandatory Signage Type— Speed Breaker cautionary sign. | Sign No. 5 (IRC:67) | Cl. 5.1 |
| Sign Placement Distance— Distance from the sign to the first speed breaker. | 40 m in advance | Cl. 5.1 |
| Sign Board Size (Normal)— Equilateral triangle for normal sized signs on minor roads. | 600 mm side triangle | Cl. 5.1 (ref. IRC:67) |
| Markings on Speed Breaker— For enhanced visibility, especially at night. | Alternating Black & White Bands | Cl. 5.2 |
| Width of Marking Bands— Bands should be of luminous paint or thermoplastic paint. | 50 cm | Cl. 5.2 |
| Lighting Requirement— Street lighting poles should be located for clear visibility at night. | Should be well-lit | Cl. 5.3 |
| Preferred Construction Material— Precast units (e.g., rubber) may also be used. | Bituminous Concrete | Cl. 6.1 |
IRC 99 (2018) provides Tentative Guidelines on the Provision of Speed Breakers for Control of Vehicular Speeds on Minor Roads — the IRC's specification for speed-table + speed-bump design to slow vehicles at sensitive locations (school zones, hospitals, residential streets, intersection approaches).
Use IRC 99 when you are: - Designing speed control measures at sensitive locations - Specifying rumble strips, speed humps, speed tables for traffic calming - Doing traffic calming in residential zones - Designing approach to school / hospital zones - Specifying speed-control on rural minor roads - Cross-referencing with IRC:SP-32:1988 (Traffic Calming Measures)
Speed control types:
1. Rumble strips (audible warning): - Series of slight ridges; transverse to traffic - Cause tyre vibration + audible noise - Speed reduction: modest - For: long uphill / fatigue zones
2. Speed humps (round or trapezoidal): - Single transverse bump; height 50-100 mm - Width: 1-2 m - Speed reduction: ~20-30 km/h - For: minor / local roads
3. Speed tables (plateaus): - Raised section with flat top; ramps on both sides - Length: 3-6 m flat top + 1-2 m ramps each side - Height: 75-100 mm - Speed reduction: significant; comfortable at low speed - For: school zones, pedestrian crossings
4. Mini-roundabouts: - Small painted circle; central island - For: residential intersections
When IRC 99 applies: - Minor roads with regular pedestrian / school activity - Approaches to intersections + railway crossings - Rural village roads passing through populated areas - NOT for high-speed NH (use signage + enforcement instead)
Speed-table design (preferred over speed-bump for vehicle comfort):
Cross-section: - Total length (with ramps): 6-9 m - Flat top: 3-6 m - Ramp each side: 1.5-3 m - Height: 75-100 mm (above pavement) - Ramp slope: 1:15-1:20 (gentle for buses + emergency vehicles) - Cross-fall on flat top: match adjacent carriageway
Speed-bump design (more aggressive): - Length (longitudinal): 0.6-1.0 m - Height: 50-75 mm - Shape: circular or trapezoidal - Speed effect: drivers slow to 15-30 km/h
Marking + signage: - Markings: white-yellow stripes on speed-table; visible at distance - Advance warning sign: placed 50-100 m before speed-control - Sign type per IRC:67:2012: warning sign + speed limit - Lighting: especially for night visibility (urban context)
Approach considerations: - Pavement transition: smooth approach (no abrupt edges) - Drainage: water doesn't pool at base of speed-table - No speed-table at intersection (cars stop suddenly at conflict) - Minimum distance from intersection: 30-50 m
Frequency on a road: - Single speed-table at known hazard location (school, hospital) - Series of speed-tables (2-3): if speed control needed continuously - Spacing between consecutive speed-tables: 100-200 m - Speed-table density: typically max 3-5 per km on minor roads
Construction materials: - Asphalt overlay: simple; ~75-100 mm thick layer - Concrete speed-table: more durable; cast-in-place RCC - Pre-fabricated rubber / plastic: quick install; less durable - Marked-only (paint speed-tables): for designer visualization but limited speed effect
Standard speed-table dimensions: - Crossing width (transverse): 3-4 m (match road width) - Height: 75-100 mm - Ramp slope: 1:15-1:20 - Flat-top length: 3-6 m - Total length (with ramps): 6-9 m
Standard speed-bump dimensions: - Length: 0.6-1.0 m - Height: 50-75 mm - Smooth radius profile to avoid vehicle damage
Speed reduction (typical): - Speed-bump: vehicles slow to 15-25 km/h - Speed-table: vehicles slow to 25-35 km/h - Rumble strip: vehicles slow to 70-80 % of approach speed - Mini-roundabout: vehicles slow to 30-40 km/h
Construction tolerances: - Height: ± 5 mm of design - Ramp slope: ± 10 % of design - Width: per road width - Marking: clean, visible
Acceptance: - Dimensions per design - Marking + signage installed - Smooth ramps without edges - Drainage functional - Pre-opening visual + signage verification
Vehicle impact: - Standard car: drive over at < 30 km/h smoothly - Standard bus: rough ride at > 25 km/h - Standard truck: rough ride; suspension stress - Emergency vehicle: slows; design for comfortable passage
Maintenance: - Annual visual inspection - Repainting of markings (every 2-3 years) - Repair / replacement of damaged speed-tables (typically every 5-10 years) - Signage refresh
Limitations of speed-tables: - Vehicle stress — buses, trucks, emergency vehicles - Driver fatigue if too many in series - Noise from vehicles passing - Surface degradation at edges over time - Not effective on high-speed roads (drivers don't reduce speed adequately)
When NOT to use speed-tables: - NH/SH high-speed roads (signage + enforcement preferred) - Emergency vehicle routes (use signs + enforcement) - Bus + truck corridors (use signs + enforcement) - Steep gradients (drainage + vehicle stress) - Without proper marking + signage (driver surprise)
1. Speed-table on high-speed road. Driver surprise; rear-end + roll-over crashes. Limit to minor roads. 2. No advance signage. Driver doesn't anticipate; impact at full speed. Mandatory warning sign 50-100 m ahead. 3. Height excessive. > 100 mm; vehicle bottoms strike; damage + complaints. 100 mm maximum height. 4. Ramp slope too steep. Sharp edges; vehicle damage. Maximum 1:15 slope; gentle. 5. No markings. Speed-table invisible at night; impact. Marked + lit per IRC:35:2015. 6. Drainage neglected. Water pools at base; aquaplaning + damage. Drainage at speed-table edges. 7. Multiple in series too close. Driver fatigue + frustration; speed-tables ineffective. 100-200 m spacing. 8. Near intersection. Vehicles stop suddenly at intersection after speed-table; rear-end. 30-50 m from intersection. 9. No coordination with adjacent road. Speed-table on minor road; major road continues at normal speed; conflict. Speed control on both / coordination. 10. Hand-built without standards. Random shapes; vehicles damaged. Per IRC 99 dimensions. 11. Materials low quality. Asphalt overlay flakes; speed-table degrades quickly. M30+ concrete or quality asphalt. 12. No road safety audit pre-installation. Mistakes discovered after construction; cost of relocation. Per IRC:SP-44:1996. 13. Removal without restoration. Speed-table removed; pavement uneven. Proper restoration after removal. 14. Cost-effectiveness not considered. Speed-table installed where signage + enforcement would work. Cost-benefit per location.
Speed control project — IRC 99 touchpoints:
1. Identification: - Crash data analysis at sensitive locations - Pedestrian / school zone identification - Resident / community input
2. Design: - Speed-table location + dimensions per IRC 99 - Marking + signage per IRC 35 + IRC 67 - Approach + transition design - Drainage consideration - Coordination with adjacent road network
3. Tender + BOQ: - Speed-table material (asphalt or RCC) - Signage + markings - Construction works
4. Construction: - Existing pavement preparation - Speed-table construction - Marking + signage installation - Quality check (dimensions, slope)
5. Pre-opening: - Road safety audit - Visual verification - Signage check
6. Operations + monitoring: - Initial speed survey (before-after) - First-month crash + complaint monitoring - Adjustments if needed (height, location, marking) - Annual maintenance
IRC 99 is the modest but important reference for traffic calming in India — applied at school zones, hospitals, residential areas, and where vehicle speed reduction is critical for safety.