Road Speed Breaker / Speed Hump Design & Calculation
A speed hump is not simply a mound of bituminous material placed across a road. It is a traffic-calming engineering measure whose height, profile, ramp geometry, location, visibility, markings, drainage and interaction with pedestrians and vehicles must be properly considered.
This article explains the design of circular humps, trapezoidal humps and speed tables, with an interactive JavaScript calculator based primarily on the geometric values of IRC:99-2018.
The commonly circulated speed-breaker infographic showing H = V² / [200(G + f)] should not be treated as a substitute for the geometry tables of IRC:99-2018.
IRC:99-2018 specifies recommended geometric parameters for circular and trapezoidal humps according to the desired speed. Therefore, the calculator below uses the IRC:99-2018 tabulated geometry rather than presenting the above expression as an IRC design formula.
- Interactive Speed Hump Calculator
- What is a Speed Hump?
- Types of Traffic-Calming Humps
- Circular Hump Design
- Trapezoidal Hump Design
- Speed Table / Raised Crossing
- Codal References
- Selection and Placement
- Signs and Road Markings
- Solved Examples
- Real-Life Engineering Applications
- Construction Considerations
- DOs and DON'Ts
- Site Inspection Checklist
- Frequently Asked Questions
Interactive IRC:99-2018 Speed Hump Calculator
Enter the desired crossing/design speed and select the hump type. The calculator performs an iterative interpolation between the IRC:99-2018 tabulated design points.
1. What Is a Speed Hump?
A speed hump is a raised portion of the carriageway designed to produce vertical deflection and encourage drivers to reduce speed.
The engineering objective is not merely to make a vehicle slow down. A properly designed traffic-calming measure should encourage the desired speed while maintaining acceptable safety, vehicle stability, drainage and visibility.
IRC:99-2018 explains traffic calming as a combination of physical and visual measures intended to reduce vehicle speeds and speed differences between road users.
- height / rise,
- profile,
- ramp gradient,
- overall length,
- target speed,
- visibility,
- signage and markings,
- location,
- traffic composition, and
- quality of construction.
2. Types of Speed-Calming Devices
2.1 Circular Hump
The longitudinal profile is based on a circular arc. The radius and chord length vary according to the desired speed.
Circular humps are useful where a continuous curved profile is preferred.
2.2 Trapezoidal Hump
A trapezoidal hump consists of two ramps and a raised flat section. The ramp gradient is selected according to the desired speed.
It is particularly useful where a raised pedestrian crossing or flat-topped traffic-calming treatment is required.
2.3 Speed Table
A speed table is a longer raised platform with ramps on either side. It can be integrated with pedestrian crossing facilities.
2.4 Rumble / Transverse Bars
Rumble treatments provide a warning or alerting effect rather than necessarily producing the same vertical deflection as a road hump.
3. Circular Hump Design as per IRC:99-2018
IRC:99-2018 provides a table of recommended radii and chord lengths for circular humps assuming a rise of approximately 100 mm.
| Desired Speed (km/h) | Radius (m) | Chord Length (m) | Bus Speed During Passage (km/h) |
|---|---|---|---|
| 20 | 11 | 3.0 | — |
| 25 | 15 | 3.5 | 10 |
| 30 | 20 | 4.0 | 15 |
| 35 | 31 | 5.0 | 20 |
| 40 | 53 | 6.5 | 25 |
| 45 | 80 | 8.0 | 30 |
| 50 | 113 | 9.5 | 35 |
The table demonstrates an important engineering concept: higher desired speeds require a substantially flatter and longer hump profile.
4. Trapezoidal Hump Design
A trapezoidal hump consists of a raised flat section and ramps on both sides. IRC:99-2018 gives the following recommended ramp geometry.
| Desired Speed (km/h) | Ramp Length (m) | Gradient | Bus Speed During Passage (km/h) |
|---|---|---|---|
| 20 | 0.70 | 14.0% | — |
| 25 | 0.80 | 12.5% | 5 |
| 30 | 1.00 | 10.0% | 10 |
| 35 | 1.30 | 7.5% | 15 |
| 40 | 1.70 | 6.0% | 20 |
| 45 | 2.00 | 5.0% | 25 |
| 50 | 2.50 | 4.0% | 30 |
Basic Geometry
- Ramp length = 1.00 m
- Gradient = 10%
- Adopted rise = 100 mm
5. Speed Table / Raised Pedestrian Crossing
A speed table is different from a short sharp hump. It provides a longer raised platform and can be integrated with a pedestrian crossing.
Where pedestrian movement is the primary concern, the designer should consider the entire pedestrian facility rather than installing an isolated hump.
For pedestrian facilities, the applicable provisions of IRC:103-2022 should also be consulted.
6. Important Codal References
| Code / Document | Application |
|---|---|
| IRC:99-2018 | Guidelines for Traffic Calming Measures in Urban & Rural Areas. Primary reference for traffic-calming measures, including circular and trapezoidal humps. |
| IRC:35-2015 | Code of Practice for Road Markings. Important for markings on speed breakers/humps and visibility. |
| IRC:67-2022 | Code of Practice for Road Signs. Relevant to warning and regulatory signage. |
| IRC:103-2022 | Guidelines for Pedestrian Facilities. Important when a hump is associated with a pedestrian crossing. |
| IRC:79-2019 | Recommended Practice for Road Delineators, relevant where delineation and night-time guidance are required. |
| IRC:86-2018 | Geometric design considerations for urban roads and speed environment. |
| MoRTH Specifications | Applicable construction, materials, workmanship and quality-control requirements shall be followed where the work forms part of a MoRTH-controlled road project. |
7. Where Should Speed Humps Be Provided?
A speed hump should be installed because a traffic-safety problem has been identified, not merely because a local request has been received.
Potential Applications
- Residential streets where operating speeds are excessive.
- Approaches to locations with significant pedestrian activity.
- Selected minor-road junction approaches.
- Locations with documented speed-related crashes.
- Approaches to selected hazardous locations where speed control is engineering-justified.
- School, hospital and institutional environments, subject to proper traffic assessment.
- Locations requiring controlled approach speed to a traffic-calming zone.
Locations Requiring Special Care
- High-speed highways.
- Routes carrying substantial bus traffic.
- Locations with poor sight distance.
- Sharp horizontal or vertical curves.
- Immediately before bridges or structures without checking drainage, structural and traffic implications.
- Locations where water will accumulate on the road surface.
- Locations where emergency vehicles require uninterrupted movement.
8. Road Markings and Signs
The physical hump alone is not a complete traffic-calming treatment. Drivers must be able to identify the hazard sufficiently in advance.
8.1 Road Markings
IRC:35-2015 contains provisions for speed-breaker markings. The markings should provide conspicuity during both day and night conditions. Retro-reflective treatment and suitable road studs may be used where specified by the applicable standard and project requirements.
8.2 Warning Signs
Warning signage should be provided in accordance with the applicable road-sign standard and site conditions.
The current IRC publication for road signs is IRC:67-2022.
8.3 Night Visibility
- Use appropriate retro-reflective markings.
- Maintain clean sign faces.
- Check visibility from actual driver approach distance.
- Provide road studs/delineation where justified.
- Ensure vegetation does not obscure the sign.
9. Solved Example 1 — 30 km/h Trapezoidal Hump
Given
- Desired speed = 30 km/h
- Hump type = trapezoidal
- Adopted rise = 100 mm
- Flat-top width = 0.60 m
Step 1 — Obtain Ramp Length
From IRC:99-2018 Table 3.2:
Step 2 — Calculate Total Length
Therefore, the geometric length of the trapezoidal hump is approximately 2.60 m for the assumed 0.60 m flat top.
10. Solved Example 2 — 40 km/h Trapezoidal Hump
Given
- Desired speed = 40 km/h
- Rise = 100 mm
- Flat-top width = 0.60 m
IRC Geometry
From IRC:99-2018 Table 3.2:
Total Length
The important observation is that the hump becomes considerably flatter and longer as the target speed increases.
11. Solved Example 3 — Circular Hump at 30 km/h
Given
- Desired speed = 30 km/h
- Circular hump
- Assumed rise = approximately 100 mm
IRC:99-2018 Table 3.1 gives:
Therefore, for a 30 km/h desired-speed circular hump, the recommended geometric parameters are approximately:
- Radius = 20 m
- Chord = 4.0 m
12. Solved Example 4 — 25 km/h Circular Hump
For a desired speed of 25 km/h, IRC:99-2018 gives:
This illustrates why the geometry should be selected from the desired speed rather than constructing a standard hump with arbitrary dimensions.
13. How the Calculator Performs Iteration
The calculator does not invent a new empirical formula. Instead, it uses the discrete IRC:99-2018 design points and interpolates between adjacent values when an intermediate speed is entered.
Example — 32 km/h Trapezoidal Hump
The IRC table gives:
For an intermediate target of 32 km/h, the calculator evaluates the fraction:
Then:
14. Real-Life Engineering Applications
Example A — Residential Street
Suppose a residential street has a measured operating speed of 42 km/h although the desired traffic-calming speed is 30 km/h.
The Engineer should not simply construct a 75 mm or 100 mm bump because it is commonly used locally. The traffic-calming objective should first be established and an appropriate hump geometry selected.
A 30 km/h trapezoidal hump would use the corresponding IRC geometry, subject to site suitability.
Example B — School Approach
A school approach may have substantial pedestrian crossing demand. Instead of an isolated sharp hump, the Engineer can evaluate a raised pedestrian crossing / speed table with appropriate signage, markings, drainage and pedestrian accessibility.
The pedestrian facility should be designed together with the traffic-calming measure.
Example C — Minor Road at a Junction
At a minor-road approach to a junction, traffic calming may be used to reduce approach speeds and improve interaction between vehicles and pedestrians.
However, sight distance, turning movements, drainage, road markings and junction geometry must be checked before construction.
Example D — Hospital Zone
A hospital zone may require lower operating speeds and predictable vehicle behaviour.
A properly designed traffic-calming scheme can combine:
- speed restriction signs,
- road markings,
- pedestrian crossing,
- raised table/hump,
- lighting,
- footpath continuity, and
- clear approach visibility.
Example E — Bus Route
Bus routes require particular attention because a short, steep hump can produce significant discomfort for passengers and dynamic effects on large vehicles.
IRC:99-2018 specifically provides bus-passage information for the recommended hump geometries. Where buses must be accommodated comfortably, the Engineer should evaluate whether a longer, flatter traffic-calming treatment or speed table is more appropriate.
15. Is 75 mm or 100 mm Height Always Correct?
No. The height cannot be selected independently of profile and target speed.
The image commonly circulated online often shows a 75 mm high hump, 600 mm top width and 1:10 slopes. Those dimensions may be useful as a local drawing concept, but they should not automatically be labelled as the universal IRC:99-2018 design.
IRC:99-2018 states that circular hump geometry is based on an assumed rise of 100 mm, while trapezoidal humps are described as having a 50–100 mm raised flat section.
H = ___ mm, Ramp = ___ m, Gradient = ___%, Flat Top = ___ m, Total Length = ___ m, Target Speed = ___ km/h
16. Construction Considerations
16.1 Existing Pavement Preparation
- Clean the existing pavement thoroughly.
- Remove loose particles and contaminants.
- Repair potholes and weak areas before hump construction.
- Ensure the underlying pavement is structurally sound.
16.2 Profile Control
One of the most common field defects is an incorrectly shaped hump. The contractor may achieve the required maximum height but fail to achieve the specified longitudinal profile.
Therefore, templates, string lines, level measurements or suitable survey equipment should be used to verify the finished profile.
16.3 Compaction
Where bituminous materials are used, proper temperature, layer thickness, rolling pattern and compaction are important.
The relevant project specifications and applicable MoRTH specifications should govern the construction methodology.
16.4 Drainage
A hump should never create an unintended water trap.
After construction, inspect the road during or immediately after rainfall where practicable.
17. Speed Hump Site Inspection Checklist
| Item | Inspection Question | Status |
|---|---|---|
| 1 | Is the location justified by a traffic-calming requirement? | ☐ |
| 2 | Is the target speed established? | ☐ |
| 3 | Is the selected hump type appropriate? | ☐ |
| 4 | Is the rise within the adopted design? | ☐ |
| 5 | Are ramp lengths correct? | ☐ |
| 6 | Is the longitudinal profile smooth? | ☐ |
| 7 | Is sight distance adequate? | ☐ |
| 8 | Are warning signs installed? | ☐ |
| 9 | Are markings visible during daytime? | ☐ |
| 10 | Are markings/road studs visible at night? | ☐ |
| 11 | Is drainage unobstructed? | ☐ |
| 12 | Is the hump compatible with bus/emergency traffic? | ☐ |
| 13 | Are pedestrians provided with safe crossing facilities? | ☐ |
| 14 | Has the finished geometry been surveyed? | ☐ |
18. DOs and DON'Ts
✓ DO
- Do determine the desired traffic-calming speed.
- Do refer to IRC:99-2018.
- Do consider road hierarchy and traffic composition.
- Do provide advance warning signage.
- Do provide conspicuous road markings.
- Do check night-time visibility.
- Do maintain adequate sight distance.
- Do provide proper drainage.
- Do consider buses, ambulances and emergency vehicles.
- Do verify the constructed profile with survey measurements.
- Do integrate pedestrian facilities where pedestrian demand is high.
- Do maintain the hump after construction.
✕ DON'T
- Don't construct an arbitrary sharp bump.
- Don't assume every road requires the same hump dimensions.
- Don't copy dimensions from an internet infographic without checking the applicable code.
- Don't use the formula shown in a social-media graphic as a substitute for IRC:99-2018 geometry.
- Don't ignore bus traffic.
- Don't place a hump where visibility is inadequate.
- Don't block drainage paths.
- Don't leave an unmarked hump at night.
- Don't create an excessively steep ramp.
- Don't ignore pedestrian accessibility.
- Don't open freshly constructed bituminous work before adequate compaction and finishing.
- Don't treat a speed hump as a replacement for proper traffic engineering.
19. Expert Engineering Observations
19.1 Height Alone Does Not Define the Hump
Two humps can have the same height but produce very different vehicle responses if their ramp/profile lengths are different.
19.2 A Shorter Hump Is Not Necessarily Better
A very short, steep hump can create excessive vertical acceleration, vehicle impact and passenger discomfort.
19.3 Target Speed Is Fundamental
The correct design question is not:
The better question is:
19.4 Traffic Composition Matters
A road carrying predominantly cars and motorcycles behaves differently from a road carrying buses, trucks and emergency vehicles.
19.5 Construction Tolerance Matters
Even a theoretically correct design can become ineffective or unsafe if the contractor constructs an abrupt transition, uneven profile or incorrect height.
20. Common Speed Breaker Design Errors
- Using the same hump dimensions everywhere.
- Ignoring design/desired speed.
- Constructing excessive height.
- Insufficient warning signage.
- Poor night visibility.
- Improper transition between existing pavement and hump.
- Creating drainage blockage.
- Using unsuitable treatment on high-speed highway sections.
- Ignoring buses and heavy vehicles.
- Failing to verify the completed geometry.
21. Conclusion
A road speed hump is a small physical element but an important traffic engineering intervention. Its success depends on much more than simply raising the pavement.
The designer should establish the required traffic-calming speed, select an appropriate type of hump, adopt geometry consistent with IRC:99-2018, provide proper signage and markings, consider pedestrians and heavy vehicles, maintain sight distance and drainage, and verify the finished construction.
22. Frequently Asked Questions
What is the recommended speed hump height in IRC:99-2018?
IRC:99-2018 uses an assumed rise of approximately 100 mm for its circular hump table and describes trapezoidal humps with a 50–100 mm raised flat section. The final adopted geometry should be selected according to the appropriate traffic-calming treatment and project requirements.
Is 75 mm height an IRC:99-2018 standard?
75 mm can fall within the 50–100 mm range described for trapezoidal humps, but the commonly circulated 75 mm / 600 mm / 1:10 combination should not automatically be described as the universal IRC:99-2018 standard geometry.
What is the IRC design for a 30 km/h trapezoidal hump?
IRC:99-2018 Table 3.2 gives a 1.0 m ramp length and 10% gradient for 30 km/h. The total hump length additionally depends on the adopted flat-top width.
What is the circular hump geometry for 30 km/h?
IRC:99-2018 Table 3.1 gives a radius of 20 m and chord length of 4.0 m for a 30 km/h desired speed, with an assumed rise of approximately 100 mm.
Can a speed hump be installed on a bus route?
Bus traffic must be specifically considered. IRC:99-2018 provides information regarding bus passage speeds for its recommended hump geometries. A longer and flatter treatment or speed table may be more appropriate depending on the site.
What code is used for speed breaker markings?
IRC:35-2015, Code of Practice for Road Markings, contains provisions for markings on speed breakers and related visibility requirements.
Which IRC code is used for road signs?
IRC:67-2022 is the current IRC publication titled Code of Practice for Road Signs.
Should a speed breaker be provided near a pedestrian crossing?
A traffic-calming treatment can be integrated with pedestrian facilities, but the complete arrangement should be designed together. IRC:103-2022 should be consulted for pedestrian-facility requirements.
23. References
- Indian Roads Congress — IRC:99-2018, Guidelines for Traffic Calming Measures in Urban & Rural Areas.
- Indian Roads Congress — IRC:35-2015, Code of Practice for Road Markings.
- Indian Roads Congress — IRC:67-2022, Code of Practice for Road Signs.
- Indian Roads Congress — IRC:103-2022, Guidelines for Pedestrian Facilities.
- Indian Roads Congress — IRC:79-2019, Recommended Practice for Road Delineators.
- Relevant project specifications and applicable MoRTH Specifications for Road and Bridge Works.
This calculator is intended for engineering education, preliminary checking and design-office assistance. It does not replace the latest edition of the applicable IRC publication, approved project drawings, traffic study, road-safety audit, authority requirements or the judgment of the Engineer responsible for the work.
Before construction, the final geometry, location, signage, markings, drainage and traffic-management arrangement should be checked and approved by the competent road authority/Engineer.
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