ASSIGNMENT PART 1
Objective
The objective of the assignment is to give you ‘hands-on' experience by undertaking a road safety engineering investigation. The assignment will help you to put into practice the material covered in each topic and give you an introduction to the challenges faced by practitioners in this area.
Outline
Select a case study site, establish the availability of relevant data and submit a report so that the suitability of the site for the assignment purposes can be assessed. Submit this part in week 3.
Criteria
You should select a site that:
- is conveniently located (as you will be travelling there often)
- you can inspect safely and easily (can you park safely?)
- is not too large or small
- you can obtain adequate data for and has an existing accident record over the past 5 years.
An example of a suitable case study site might be:
- an urban or rural intersection
- a rural or urban mid-block
- an area, such as a local traffic precinct (but not too big).
It is highly likely that you will have to initially select a number of sites, progressively produce a shortlist of suitable sites as you see what data are available and select the ‘best' site for further study. It is worth briefly reading through Topics 5 and 6 before you make your final decision, as you will find it easier to develop countermeasures for your site if there is a reasonably clear pattern to the accidents.
Data
You will need to collect as much data as possible about the site to understand why accidents are occurring. This could include:
- a base plan of the location (you may have to draw it yourself)
- crash data/records from the responsible road authority (state or local) or internet1
- traffic volumes, composition and speeds at the site
- traffic strategies (bus, truck, bike etc) if they exist
- an inventory of road characteristics (widths, no. of lanes etc) and traffic control items
- results of on site observations etc.
You will also need to be familiar with the site surrounds - accidents don't just happen because of what is only at the site itself.
Site Investigation Safety Assessment
There is always a need to ensure the personal safety of field survey staff during a site inspection, and that of other road users and the community in general. Appropriate measures must be taken to address any risks to which they may be exposed.
As part of this assignment, you will need to undertake site inspections in the road environment. As such, it is necessary to think about any hazards to you, your assistants (if any) and other road users your data collection activities may entail. The level of risk associate with each hazard can be assessed in terms of its consequence (that is, the severity resulting from an uncontrolled hazard) and its probability of occurrence.
The consequences of different risks could be graded as:
- catastrophic, resulting in multiple loss of life
- major injury, resulting in death or permanent incapacity
- severe injury, requiring extensive medical treatment and/or hospitalisation
- moderate injury, requiring medical attention
- minor injury, requiring first aid or short term discomfort.
In a similar manner, the probability of occurrence could be assessed on a four-point scale:
- frequent: repeated occurrence
- probable: may occur several times
- occasional: may occur sometimes
- remote: not likely to occur.
The level of risk is useful for identifying priority areas for attention, particularly where there are life-threatening hazards. Risks can be controlled, perhaps through choice of the site, operational procedures, training, safety equipment, or a combination of these.
Before exposing yourself to any risk, you should undertake a safety assessment and implement suitable risk controls, to reduce the chances of injury during your data collection. As part of this assignment, you must explicitly outline all possible risks, their consequence and probability of occurrence. For each of these, you must detail how you plan to control them.
ASSIGNMENT PART 2
Outline
For the site selected and approved in Assignment Part 1, undertake a road safety engineering investigation to determine the causes of the crashes, propose countermeasures and evaluate their cost effectiveness. There are three main tasks to this part of the assignment, but only one submission in week 10.
Discuss this submission with your lecturer
The work to finalise this submission is a significant part of your learning and assessment. You will not be able to put it all together just in week 10 and will need to continually work on it between weeks 3 and 10. If you have questions about how to go about this part of the assignment (or others), it is vital you contact your tutor for advice and/or to provide him/her with updates of your progress.
Task A
Obtain the traffic accident data for your case study area and present them in a form which shows locations and accident types.
1. You will need to obtain all the traffic accident information for your area if you haven't already done so (see Assignment Part 1).
When obtaining the information you will have to decide for what period you require the information. You will always require the latest available information (unless, for example, you are trying to make direct comparisons with other areas which have been studies earlier). You will probably require at least three years' information to minimise the effects of fluctuations caused by seasonal, isolated or random events. Note that these effects cannot always be entirely removed and that the number of recorded accidents does not equal the number of accidents actually occurring. Consequently, caution should be applied when drawing conclusions about the specific number and type of accidents at any location.
If a substantially greater period of data (beyond three years) is available, you should consider whether the oldest data is still relevant. For example, have there been any changes in the road network or land use within the area or nearby which could affect travel patterns and therefore affect the level of accidents? These might include a major new development, a new set of signals, a road widening, or treatment of an accident blackspot. Also, has there been any change to driving rules or to the ways in which accident data has been recorded or produced in recent years? If so it would be worthwhile obtaining data which is consistent, so long as it is for at least three years and is sufficiently up to date to be relevant.
When seeking information for particular streets and intersections, be aware of how the information is recorded. If there are three street names intersecting at one intersection, is the information recorded using only the two lowest-order alphabetic street names (or do any of the roads go by two names like Princes Highway and Main Street)? Do you have to ask for street lengths as well as intersections? Remember to include boundary roads and intersections which are within the case study area agreed to at the start of the unit.
2. Present the information for the whole period you have chosen. You will need to transfer the information into a base map (or maps) of the area. Consider what are the important categories to differentiate diagrammatically.
How will you show the different numbers of accidents at the site?
Accident severity is usually a worthwhile category to indicate, as it can assist in evaluating the cost of accidents and therefore the cost-effectiveness or remedial treatments. Severity is categorised in terms such as ‘fatal', ‘injury' and ‘property damage'. The latter means there are no recorded injuries. The term ‘casualty' means ‘fatals plus injuries'.
Most accident recording systems indicate accident type, in terms of the movements the road users were making prior to or when the accident occurred (see Figure 6.57.2.3, in Section 6.2 of Traffic engineering and Management). Depending on the nature of your case study area, you should attempt some indication of the types of road users and/or the movements they were making.
Further, look at the accident data and see if there are any other recorded details which stand out (e.g. is there an over-representation of accidents involving wet weather, night- timer or pedestrians?).
3. Undertake further investigation as necessary (see Topic 6). Does a pattern of driver behaviour begin to form? Can you see why accidents are happening? Write a clear summary of what the cause of the accidents appears to be.
Task B
Develop countermeasures for your site.
1. If your site has one or more hazardous road locations, choose one for remedial treatment. If your investigations in Part A resulted in an assessment that there was no hazardous road locations, you will need to notionally add more accident statistics to it to bring it to a level of hazard which meets your adopted criteria. When doing this, add accident types which might typically apply to this type of location. For example:
Signalised intersections:
rear end, right turn against oncoming traffic and/or cross traffic
Local intersection:
cross traffic
Shopping centre car park:
parking or unparking, intersection accidents and/or pedestrian emerging
Urban arterial road:
hit pedestrian, run into parked vehicle, side swipe and/or off carriageway
Rural Road:
head-on, off carriageway on bend and/or off carriageway into fixed object.
2. Develop a package of countermeasures for the site. You will again need to inspect the site to assist you in deciding what factors may have contributed to the particular accident problem. Inspect it from the point of view of the road users involved (e.g. unfamiliar car driver, pedestrian, bicycle rider, etc.). Remember that there may be road users with particular characteristics at this location (e.g. the pedestrians are young as it's near a school).
To assist in developing countermeasures, read the relevant sections of Topic 7.
3. During your on-site inspections, you may also become aware of some causes of potential hazard which have not resulted in recorded accidents. (e.g. there may be a tree which is blocking a set of signal lanterns, but this is not resulting in accidents yet as the combination of weather, globes in the other lanterns burnt out and/or trucks blocking visibility has not occurred yet). Road safety audits are discussed in Topic 12 as a means of identifying potential hazards before accidents occur.
Task C
Assess the cost-effectiveness of the remedial treatments for your hazardous road location, which you developed in Task B.
1. Make a cost estimate of all the works involved in your proposed remedial treatment. You should be able to obtain unit cost rates for typical elements of civil engineering construction from your local Council engineering officer or, failing that, from your state road and traffic authority office which deals with estimating for accident blackspot treatments.
However, do not spend a great deal of time on this. If cost estimates cannot be readily obtained, make a (realistic) guess at the likely cost of works. The point of this exercise is to demonstrate the application of cost-benefit analysis, not to develop skills in estimating the cost of civil engineering works, so we don't want you to spend much time on this.
2. Using the techniques outlined in Topic 7, estimate the value of the crashes which are occurring at the site and which the proposed treatment is likely to reduce. (Do not include accidents which are unlikely to be affected by the proposed treatment.)
Are there any accident types which are likely to increase after the treatment goes in (e.g. signalisation of a crossroad usually reduces the incident of right angle accidents which can be costly in terms of injuries and damage, but it often leads to an increase in rear-end accidents which are less costly)?
3. Using the results of (1) and (2) above, calculate the net present value (NPV) and benefit/cost ratio (BCR) of the proposed remedial treatment. To do this you will have to determine the likely annual cost reduction following treatment over the evaluation period (which you will need to estimate), reduce to a net present value, and incorporate the capital cost of treatment.
If the treatment proves to have a negative NPV (or BCR of less than 1.0), report on whether there is any part of the treatment which could be revised to improve the result. Does this involve a greater or lesser reduction in accident numbers? How many additional similar accidents would need to occur to make the treatment worthwhile?
If the treatment has a positive NPV (or BCR greater than 1.0), what is the minimum level of accident at what the project could be considered cost-effective?