Dynamic Risk Assessment vs RAMS: Key Differences Explained

Most UK construction sites use both documents. Most guidance treats them as opposites. Neither framing is right — and getting it wrong exposes contractors to enforcement action, civil liability, and, most importantly, avoidable injuries.

This page grounds the distinction in the Construction (Design and Management) Regulations 2015 (CDM 2015, SI 2015/51) — the principal UK statutory instrument governing health and safety management on construction projects — and uses a single, concrete worked scenario to show how both documents operate simultaneously on the same task.

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What is a RAMS?

RAMS — Risk Assessment and Method Statement — is an industry term, not a statutory phrase. CDM 2015 does not use the acronym. What CDM 2015 does require is that construction-phase planning documents are produced: a construction phase plan must be prepared before work begins, and contractors carry duties to plan, manage, monitor and coordinate the health and safety of construction work.

In practice, a RAMS is the document package that satisfies those duties at the task level. The risk assessment identifies hazards, evaluates likelihood and severity, and records the controls to be applied. The method statement describes the sequence of work, the equipment to be used, the competencies required, and the emergency arrangements. Together they constitute the pre-planned, written control framework for a defined task.

RAMS are produced before the task starts, by a competent person with knowledge of the specific work, and reviewed and accepted by the principal contractor before operatives begin.

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What is a Dynamic Risk Assessment?

A dynamic risk assessment (DRA) is not defined in statute. It is a recognised good-practice tool, described in HSE guidance, that reflects the reality that conditions on site change and that workers must be equipped to respond to hazards that were not foreseeable at the planning stage.

A DRA is the real-time mental and physical process by which a worker or supervisor stops, observes changed or unexpected conditions, assesses the new hazard, applies immediate controls, and decides whether it is safe to continue. It is triggered by an unexpected event — not by the start of a task.

The critical point: a DRA does not begin with a blank sheet. It begins with the existing RAMS as its baseline. The operative asks: does this new situation fall within the controls already specified? If yes, work continues under those controls. If no, a decision must be made about whether to stop, who to escalate to, and whether the RAMS must be revised before work resumes.

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The Core Difference: Pre-Planned Control vs Real-Time Judgement

Dimension	RAMS	Dynamic Risk Assessment
When produced	Before the task begins	At the moment an unexpected change occurs
Who produces it	Competent person / H&S advisor, reviewed by PC	The worker or supervisor on the ground
Regulatory hook	CDM 2015 construction-phase planning duties	General health and safety law duty of care; HSE good practice guidance
Documentation standard	Written, signed, version-controlled, retained	Brief written record recommended; verbal where writing is impractical but documented as soon as possible
Review trigger	Change in scope, method, site conditions, or post-incident	Automatically expires once the unexpected condition is either resolved or escalated to a RAMS revision
How it interacts with the other	Provides the baseline controls the DRA measures against	Either confirms existing RAMS controls are adequate, or flags that the RAMS must be revised

The RAMS sets the boundary. The DRA tells you whether you are still inside it.

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When RAMS is Mandatory and a DRA Is Not Enough

For any construction task that is planned in advance, involves significant risk, and falls within CDM 2015's construction-phase planning framework, a pre-planned RAMS is the appropriate document. A DRA alone is not a substitute.

CDM 2015 Schedule 3 sets out categories of work involving particular risks — including work that puts workers at risk of burial under earthfalls, and work near high voltage power lines. Any task touching these categories demands thorough pre-planned assessment and method documentation before operatives are exposed to the hazard. A DRA produced on the spot cannot replace that advance planning, because the purpose of pre-planning is precisely to prevent the worker from being placed in a dangerous situation without adequate controls already in place.

Beyond Schedule 3, RAMS are contractually required on virtually every CDM-notifiable project and are standard practice across the industry for all but the most routine, low-risk tasks. Where a principal contractor's pre-construction information identifies specific site hazards, the subcontractor's RAMS must address those hazards explicitly — something a field DRA cannot achieve retroactively.

A DRA is not enough when:

• The task is planned and the risks are foreseeable at the planning stage
• The work falls within a high-risk category under CDM 2015 Schedule 3
• The principal contractor or client requires RAMS as a contract condition
• The change in conditions is significant enough that existing RAMS controls no longer apply

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When a DRA Is the Right Tool — and What It Must Still Include

A DRA is appropriate when conditions change unexpectedly during an otherwise well-planned task and the change is within the supervisor's authority to manage without stopping all work. Typical triggers include:

• A new hazard appearing mid-task (unexpected ground conditions, uncharted services, weather deterioration)
• A planned control proving impractical on the day (access point blocked, equipment substituted)
• A near-miss or incident that requires an immediate reassessment before work continues

Even when the DRA is verbal and immediate, it must still be documented as soon as practicable. An undocumented DRA is indistinguishable from no assessment at all if something goes wrong.

A DRA must always include:

1. A description of the changed condition or new hazard
2. Who is at risk and how
3. The immediate control measures applied
4. The residual risk level (Low / Medium / High)
5. The authorising supervisor's name, signature, and the date/time
6. A note on whether the parent RAMS remains valid or must be revised

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Can a DRA Replace a RAMS? The Legal and Practical Answer

No. A dynamic risk assessment is a supplementary tool that operates within the framework established by a pre-planned RAMS — it does not replace it.

Under general health and safety law, risk assessments must be suitable and sufficient. For planned construction work covered by CDM 2015, foreseeable hazards should be assessed, planned and communicated before workers are exposed to risk. A judgment made in the field by a supervisor under time pressure cannot replace that advance planning for hazards that should have been identified before work started.

Practically, a subcontractor who attends site without RAMS for a CDM-notifiable high-risk task and argues that their operative's DRA was sufficient will face immediate difficulty with the principal contractor, potential enforcement by HSE, and significant civil liability exposure if an incident occurs.

The two documents are complementary. Every significant planned construction task should have a task-specific risk assessment and safe method, commonly issued as RAMS where a PC or client requires it. Some tasks will also generate a DRA during execution. Where a DRA reveals that the RAMS no longer adequately addresses site conditions, the RAMS must be revised and accepted through the site's change-control process before the affected work continues.

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Worked Scenario: Buried Live Cable During Excavation

Scenario: Groundworks operative discovers an unmarked live electrical cable mid-excavation

What the RAMS already says

The subcontractor's RAMS for the excavation task covers: trial holes at 250 mm depth intervals; hand-digging within 500 mm of identified service routes; cable avoidance tool (CAT) scan required before any mechanical excavation; emergency stop procedure if suspected services encountered; competent supervisor on site at all times.

The pre-construction information from the principal contractor noted gas and water services but did not identify electrical cables in this location.

What triggers the DRA

At 900 mm depth, the operative's CAT scanner signals. Mechanical excavation stops immediately (compliant with the RAMS). Hand investigation reveals a grey-sheathed cable — uncharted, origin unknown, potentially live.

The existing RAMS controls have been followed to this point. But the RAMS does not address the specific response to an uncharted cable of unknown voltage. The operative is now at the boundary of the RAMS's coverage.

Who acts, and how

The supervisor initiates a DRA on the spot:

1. Stop work — all personnel clear the excavation
2. Identify the hazard — uncharted cable, unknown voltage, possibly live
3. Persons at risk — groundworks operative, banksman, adjacent trades within 6 m
4. Immediate controls applied — 6 m exclusion zone established; DNO (Distribution Network Operator) emergency line called; area cordoned with barrier tape; no further excavation in a 3 m radius
5. Residual risk rating — HIGH until DNO confirms status
6. Escalation — principal contractor notified; work in affected area suspended

The supervisor completes a DRA record (see template below) and signs it. The time is logged.

Does the original RAMS need revising?

Yes. The DRA has revealed a condition not covered by the parent RAMS. Before excavation resumes in this area, the RAMS must be updated to include: confirmed cable route and voltage from DNO records; revised dig method around the confirmed service; additional CAT scan protocol; and PC sign-off on the revised document. Work resumes only after the revised RAMS has been accepted by the principal contractor.

The DRA record is retained alongside the revised RAMS in the site health and safety folder.

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Decision Flowchart: DRA Alone, or Produce/Revise RAMS First?

When an unexpected condition arises on site, work through these five questions in order:

Q1: Is there an existing RAMS or equivalent task-specific risk assessment and safe method for this task?
    └── NO  → STOP. Do not proceed with significant construction work until the foreseeable risks and safe method have been assessed, recorded and accepted through the site's pre-start process.
    └── YES → Go to Q2

Q2: Does the new/changed condition fall within the hazards and controls already described in the RAMS?
    └── YES → Apply existing controls. Record the observation. Continue work.
    └── NO  → Go to Q3

Q3: Is the new hazard within the supervisor's authority to control immediately (low/medium residual risk)?
    └── YES → Complete a DRA record. Apply additional controls. Go to Q4.
    └── NO  → STOP all work in affected area. Escalate to PC. Do not proceed to Q4.

Q4: After applying DRA controls, does the task method need to change?
    └── NO  → Continue work. Retain DRA record. Flag for RAMS review at next planned revision.
    └── YES → Go to Q5

Q5: Can the method change be managed within the existing RAMS with a minor documented amendment?
    └── YES → Amend RAMS, obtain PC acceptance where a PC is appointed, retain both DRA record and amended RAMS. Resume.
    └── NO  → Full RAMS revision required. Work in affected area suspended until revised RAMS accepted.

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DRA Record Template

Print and keep in site H&S folder alongside parent RAMS.

Field	Entry
Project / Site address
Task description
Location on site
Date and time of DRA
Changed condition / new hazard identified
Persons at risk
Immediate controls applied
Residual risk rating (circle)	LOW / MEDIUM / HIGH
Is parent RAMS still adequate?	YES / NO — if NO, state action required:
Action required
Escalated to PC? (Y/N and name)
Authorising supervisor — name
Authorising supervisor — signature
Time work resumed / remained suspended

This template is designed to sit inside the site H&S folder alongside the parent RAMS. It does not replace the RAMS — it supplements it. Review and adapt to your site, task and contractor requirements.

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Common Mistakes UK Contractors Make When Choosing Between the Two

1. Treating DRA as a shortcut to avoid writing a RAMS Arriving on site without task-specific pre-planning and completing a DRA instead is not an acceptable substitute for pre-planned high-risk work. It will fail PC review and may indicate that CDM 2015 construction-phase planning duties have not been met.

2. Assuming the RAMS covers every scenario so a DRA is never needed No RAMS anticipates every site condition. Operatives who lack DRA training and authority may continue working in an unsafe changed condition because they believe "the RAMS says it's fine."

3. Not documenting the DRA A verbal DRA with no written record leaves the contractor unable to demonstrate that a reassessment took place. Documentation takes five minutes; an undocumented DRA is worthless in an investigation.

4. Completing a DRA but not revising the RAMS when required If the DRA reveals that the task method must change, that change must feed back into a revised RAMS before work continues. A DRA record that contradicts the live RAMS creates a dangerous inconsistency.

5. Confusing DRA authorisation levels Not every DRA sits within a site operative's authority. A HIGH residual risk finding must be escalated to the PC. Failing to define those escalation thresholds in advance — ideally in the RAMS itself — is a common gap.

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How ramsdocs Supports Both Pre-Planned RAMS and On-Site DRA Documentation

ramsdocs generates PC review-ready RAMS documents designed to reduce RAMS rework during pre-construction approval. Each RAMS produced through ramsdocs includes a clear scope of work, a hazard register with control hierarchy, and an emergency/escalation procedure — giving site supervisors a defined baseline against which any in-field DRA can be measured.

The DRA record template above is available as a downloadable PDF through ramsdocs, formatted to sit alongside any RAMS in a site H&S folder.

All documents generated through or downloaded from ramsdocs must be reviewed and adapted to the specific site, task, and contractor by a competent person before use. ramsdocs does not guarantee regulatory compliance or principal contractor acceptance.

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Frequently Asked Questions

What is the main difference between a dynamic risk assessment and a RAMS? A RAMS is a pre-planned, written document produced before a task begins, covering foreseeable hazards and the controls to manage them. A dynamic risk assessment is a real-time reassessment triggered by an unexpected change in conditions during work. The RAMS sets the framework; the DRA determines whether you are still operating within it.

Is a dynamic risk assessment a legal replacement for RAMS on a CDM-notifiable project? No. CDM 2015 (SI 2015/51) imposes construction-phase planning duties that require pre-planned documentation for construction work. A field DRA cannot satisfy those duties for foreseeable, planned-for risks. The two documents are complementary, not interchangeable.

When must RAMS be produced in advance, and when is a DRA sufficient? Task-specific RAMS, or equivalent risk assessment and safe method documentation, should be produced in advance for any planned, foreseeable-risk construction task — and RAMS are required where the principal contractor requires them by contract. A DRA is sufficient only for responding to unexpected, unforeseeable changes that arise during an otherwise assessed task, and only where the residual risk after applying immediate controls is within the supervisor's authority.

Can a dynamic risk assessment be documented, and if so, how? Yes — and it should be. The one-page DRA record template above captures the hazard, persons at risk, controls applied, residual risk rating, supervisor sign-off, and whether the parent RAMS needs revision. Retain it in the site H&S folder alongside the parent RAMS.

Do subcontractors need both a RAMS and a DRA for the same task? They need task-specific risk assessment and safe method documentation in advance of every significant planned task, commonly submitted as RAMS. Whether a DRA is also generated depends on whether unexpected conditions arise during execution. On any complex construction task, it is entirely normal for both records to exist — the RAMS as the standing control framework and one or more DRA records documenting specific in-field responses.

What are the consequences of relying solely on a DRA where RAMS are contractually required? Immediate consequences include rejection by the principal contractor and suspension of work. If an incident occurs, the absence of pre-planned risk assessment and safe-method evidence will be a central finding in any investigation and will significantly weaken the contractor's position in any civil claim. It may also indicate a breach of CDM 2015 construction-phase planning duties.

What does CDM 2015 Regulation 15 actually require contractors to do regarding risk assessment? Under CDM 2015 Regulation 15(2), a contractor must plan, manage and monitor construction work carried out by the contractor or workers under the contractor's control, to ensure that, so far as is reasonably practicable, it is carried out without risks to health and safety. Separately, general health and safety law requires employers to carry out a risk assessment and record significant findings where five or more people are employed. In practice, a task-level risk assessment — typically forming the 'RA' half of a RAMS — is the standard mechanism by which contractors demonstrate they have discharged the Regulation 15(2) planning and management duty before workers are exposed to a hazard.

Does CDM 2015 Regulation 15 require a written record of risk assessments? Regulation 15 itself sets out the duty to plan, manage and monitor construction work; the obligation to record significant findings flows from the general risk assessment duty applicable to employers. Where five or more people are employed, those significant findings must be recorded in writing. For contractors on any CDM-notifiable project, producing a documented risk assessment is not a formality — it is the practical evidence that the Regulation 15(2) duty has been taken seriously, and it forms the baseline from which any DRA must operate if conditions change during the task.

What does competency look like in practice for someone conducting a DRA on site? There is no single statutory qualification for DRA competency, so firms should define it through their own safe systems of work. In practice, the person conducting a DRA should have a thorough working knowledge of the task's parent RAMS, understand the hierarchy of controls, be able to identify when a new hazard falls outside the scope of existing controls, and know at what point to escalate rather than proceed. They also need sufficient site authority to stop work — someone who lacks the confidence or seniority to halt an activity when a DRA flags unacceptable residual risk cannot exercise that judgement effectively.

How should a principal contractor assure itself that operatives are competent to conduct DRAs? Competency assurance typically runs through a combination of induction, toolbox talks, task-specific briefings, and a defined authorisation matrix that specifies which grades of supervisor may sign off a DRA and under what circumstances. At minimum, any operative expected to conduct a DRA should be able to demonstrate familiarity with the relevant RAMS, understand how to complete the site's DRA record form, and know the escalation route when a situation exceeds their authority level. Reviewing how subcontractors train and authorise their personnel to conduct DRAs is a reasonable step for a principal contractor managing construction-phase health and safety under its Regulation 15 obligations.

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This page provides general guidance only. All documents must be reviewed and adapted to the specific site, task, and contractor by a competent person before use. Nothing on this page constitutes legal advice.