Promoting Clean Urban Public Transportation and Green Investment in Moldova

Annex B. Explanatory guide for using the OPTIC Model

Purpose of the OPTIC Model

The spreadsheet-based Optimising Public Transport Investment Costs (OPTIC) Model is a simple, easy-to-use decision support tool prepared by the OECD to support the Government of Kyrgyzstan in preparing and estimating the costs and environmental benefits of the Clean Public Transport (CPT) Programme. It was used in particular for costing the replacement of the old bus fleet in urban centres with modern buses equipped with engines that run on:

• compressed natural gas (CNG)

• liquefied petroleum gas (LPG)

• diesel, ideally (imported) Euro 5 fuel

• electricity (trolleybuses and battery-powered trolleybuses)

The OPTIC Model was used to estimate programme costs, and the emission reductions of carbon dioxide (CO₂) and other pollutants from urban public transport – i.e. carbon monoxide (CO), nitrogen oxides (NO_x), particulate matter (PM) and sulphur dioxide (SO₂) – that could potentially be achieved by implementing the proposed project pipelines.

Similar models that exist on the market estimate the greenhouse gas (GHG) emission reductions for a country or for groups of countries. These models mainly focus on GHG emissions from industry and take into account various scenarios for the country’s economic development. Such models, however, are not particularly suitable for this investment programme, which focuses on reducing emissions from urban public transport only.

Preparations for using the OPTIC Model

The OPTIC Model consists of seven modules: 1) assumptions; 2) emission factors; 3) transport sector overview with information on current bus fleet and age; 4) determining the subsidy level; 5) cost calculation; 6) emission reductions calculation; and 7) programme costing and environmental effects.

Assumptions

The model has been prepared in Excel and uses macros. Therefore, when starting the model, the macros in Excel should be enabled. This requires setting the security settings to "medium". For earlier versions of Excel (before 2010), security settings can be changed using the following commands: Tools>Macros>Security. For Excel 2010 and 2013, the macro security settings can be set in the "Developer" tab. If the Developer tab is not visible, it can be accessed by going to: File>Options>Customize Ribbon and then selecting “Developer” from the options in the right-hand window.

The user needs to fill in the cells that are highlighted yellow in the Excel sheets. Then these steps should be followed:

1. Complete the information on assumptions and emission factors. Assumptions can be found under the “Assumptions” tab. The following information is essential for the model:

• the average price of a new CNG bus

• the average price of a new LPG bus

• the average price of a new diesel bus equipped with a Euro VI engine

• the average price of a new trolleybus

• the average price of a new CNG minibus

• the average price of a new LPG minibus

• the average price of a new diesel minibus equipped with a Euro VI engine.

For the purpose of this model, the average bus is understood to be a 10-metre-long bus with a total capacity of about 100 passengers.

1. Input the average level of fuel consumption for each type of bus listed above. This information should also be provided for old diesel buses that will be replaced. For the purpose of the model, old diesel buses are divided into several categories: new and more than 5, 10 and 15 years old.

2. Input fuel costs for each type of bus. The average kilometres per vehicle per day (kpvpd) ¹, which is found in the last column in Table B.1, is essential.

Table B.1. Basic assumptions: bus prices and fuel consumption

	Unit price	Fuel consumption		Fuel price		kpvpd	Fuel costs
	MDL mln		Unit		Unit		MDL/vehicle/day
New CNG bus	5.2	38.5 (53.7 m3/100 km)	kg/100 km	8.9	MDL/kg	200	684.4
New LPG bus	4.73	35.7 (70 kg/100 km)	l/100 km	10.6	MDL/l	200	755.0
New diesel Euro VI bus	4.52	50.0	l/100 km	16.5	MDL/l	200	1 651.0
New diesel standard bus	1.04	45.0	l/100 km	16.5	MDL/l	200	1 485.9
Old diesel bus > 15 years	n.a.*	56.3	l/100 km	16.5	MDL/l	200	1 857.4
Old diesel bus > 10 years	n.a.*	51.8	l/100 km	16.5	MDL/l	200	1 708.8
Old diesel bus > 5 years	n.a.*	49.5	l/100 km	16.5	MDL/l	200	1 634.5
Trolleybus	5.2**	100.0	kWh/100 km	2	MDL/kWh	200	400.0
New CNG minibus	2.02	9.6	kg/100 km	8.9	MDL/kg	200	371.5
New LPG minibus	2.02	8.93	l/100 km	10.6	MDL/l	200	188.8
New minibus equipped with a Euro 6/VI engine	2.02	11.25	l/100 km	16.5	MDL/l	200	171.1

Note: * The CPT Programme does not foresee purchase of used vehicles; ** average price for trolleybuses and trolleybuses with batteries.

Source: OECD, OPTIC Model.

Emissions factors

After inputting information on the basic assumptions, next the user inputs information on emissions from buses. This can be found under the “Emission factors” tab. The emissions will be identified in kilograms or grams of the emitted pollutant per kilometre of bus operation. The information on emissions is key for calculating emission reductions (Table B.2).

Table B.2. Assumed emission factors according to emission norms (per km)

	CO2 (kg/km)	CO (g/km)	NOx (g/km)	PM2.5 (g/km)	SO2 (g/km)
Diesel Euro 2	1.0812	2.4400	10.7000	0.2200	0.2050
Diesel Euro 2>5 years	1.1893	2.6840	11.7700	0.2420	0.2255
Diesel Euro 2>10 years	1.2974	2.9280	12.8400	0.2640	0.2460
Diesel Euro 2>15 years	1.4056	3.1720	13.9100	0.2860	0.2665
Diesel Euro VI	0.7632	0.2230	0.5970	0.0023	0.0205
CNG (EEV standard)	0.9350	0.2400	2.5000	0.0050	0.0000
LPG	1.0258	1.9200	5.0000	0.0050	0.0652
Trolleybus	0.3384	0	0	0	0
Minibus Euro VI	0.1908	0.0558	0.1493	0.0006	0.0051
Minibus Euro II	0.3514	0.7930	3.4775	0.0715	0.0666
Minibus LPG	0.2564	0.4800	1.2500	0.0013	0.0163

Source: OECD, OPTIC Model.

There are two tables containing emission factors:

• normative emissions according to the standards

• real emissions according to actually measured emissions

The source of information and the reason for providing two different sets of emission factors are discussed at the end of this annex.

Transport sector overview

Next, the information on the existing urban public sector in Moldova needs to be provided under the “Transport” tab (Table B.3). This is done by providing information on the existing bus fleet in Moldova. The fleet will be divided by bus type. The last two columns contain information on the availability of CNG stations. This information is provided by entering “Yes” or “No” into the respective cells.

Table B.3. Public transport and transport infrastructure in Moldova

Type	City	Buses					Potential for replacement			Existing CNG stations	Existing trolleybus network
					Fuel
		Bus	Mini-bus	Trolleybus	Diesel	Electricity	Bus	Minibus	Trolleybuses
Urban	Chisinau	28	618	366	646	366	59	309	50	Yes	Yes
Urban	Balti	20	52	48	72	48	15	26	12	Yes	Yes
Sub-urban	Chisinau	132	672	0	804	0	173	336	0	Yes	No
Sub-urban	Balti	28	64	0	92	0	29	32	0	Yes	No
Inter-city	Chisinau	11	3 096	0	3 107	0	318	1 548	0	Yes	No
Inter-city	Balti	11	86	0	97	0	17	43	0	Yes	No
Inter-city	Other regions	8	2 724	0	2 732	0	279	1 362	0	No	No
Total		238	7 312	414	7 550	414	891	3 656	62

Source: OECD, OPTIC Model.

Determining the subsidy level

The module on determining the subsidy level takes into account both the investment costs and savings for public service providers by replacing old buses. New buses using alternative fuels are more efficient because of technological improvements and also due to the lower price of CNG and LPG fuels compared to diesel.

The module takes into account the fact that the investments should generate at least a minimum return for public transport providers; thus, the social discount rate is used to determine the net present value (NPV) of the project. The subsidy is then determined at the level at which NPV is equal to zero (see Box B.1). The economic significance of this calculation is that the subsidy will encourage potential beneficiaries to participate in the CPT Programme without encouraging the beneficiary to make a profit based on the subsidy. The various calculations required to establish the subsidy level for CNG buses are presented in Table B.4 and Table B.5.

Box B.1. Determining the optimal subsidy level

The subsidy should be sufficient to attract potential investors/beneficiaries to apply for support from the CPT Programme, but without making the projects too profitable. This approach to calculating the subsidy will enable the government to avoid over-investing, while at the same time provide an investment incentive for potential beneficiaries without making it too profitable for them as investors. Essentially, the subsidy level should provide just the necessary leverage for individual potential beneficiaries to invest in clean transport.

In order to evaluate a given project, the net present value (NPV) is calculated by totalling the expected net cash flows (cash inflows, or receipts, minus cash outflows, or expenses) over the project operating period and discounting them using a rate that reflects the costs of a loan of equivalent risk on the capital market. An investment will yield a profit if the NPV is positive. All measures that yield a positive NPV using a discount rate that corresponds to the applied rate of return can be deemed beneficial.

The NPV is calculated as in the following formula:

where:

- NCF_i is the net cash flow in the i-th year

- r is the discount rate.

Using discounting considers two factors: the investor’s expectations with respect to the measure and that the NPV can be greater than zero during the operating period.

The calculation of the subsidy level should be based on economic principles. If the project is socially significant rather than profitable for the beneficiary, the subsidy should make a small amount of profit. In simple terms, the financial NPV including the subsidy should be approximately at the level of zero KGS, which means that the project yields an acceptable rate of return for the investor/project promoter (revenues from fares combined with lower operating costs).

The “determination of the subsidy level” module uses this principle by making a simple financial analysis of the cash inflows and outflows in each year of the analysis. Cash inflows (receipts) generated by the project include fuel savings expressed in terms of the money saved by customers (public transport providers). In terms of cash outflows (expenses), the simple financial analysis totals the difference between the investment costs of a clean and a traditional bus calculated in the other modules. In the subsidy module, the subsidy is included on the cash outflow side as a negative value.

It was assumed that the investments will be made during the first year of the project and the savings averaged over the nine years of operation. The period of analysis is 10 years, a typical lifetime for this type of project. The subsidy is calculated so that the result of the NPV calculation is equal to zero KGS.

First, the savings on fuel costs were calculated, given the lower price of CNG. The parameters used to calculate fuel savings are presented in Table B.4.

The cost of a new CNG bus (EUR 255 000; MDL 5.2 million) was compared with the average cost of a used bus (MDL 1.04 million), which beneficiaries would have been likely to purchase in the absence of public support (Table B.5).

Table B.4. Assumptions for calculating the level of public support for CNG buses

	Fuel consumption	Fuel price	Annual distance	Fuel costs per year MDL
CNG bus	38.5 kg/km	8.9 MDL/kg	46 000 km	157 000
Old diesel bus (> 15 years)	56.3 l/100 km	16.5 MDL/l	46 000 km	427 000
Annual difference				270 000

Source: OECD, OPTIC Model.

Table B.5. Calculation of the level of public support for CNG buses

(MDL)

Year	0	1	2	3	4	5	6	7	9
Investment costs for a new bus	5.2 million
Difference in price compared to a standard bus	4.16 million
Required public support	2.241 million
Annual fuel cost savings	270 000	270 000	270 000	270 000	270 000	270 000	270 000	270 000	270 000
NPV	0

Source: OECD, OPTIC Model.

Similar calculations are made for LPG buses (Table B.6 and Table B.7) and for modern diesel buses (Table B.8 and Table B.9).

Table B.5. Assumptions for calculating the level of public support for LPG buses

	Fuel consumption	Fuel price	Annual distance	Fuel costs per year, MDL
LPG bus	35.7 l/100 km	10.6 MDL/l	46 000 km	174 000
Old diesel bus (> 15 years)	56.3 l/100 km	16.5 MDL/l	46 000 km	427 000
Annual difference				245 000

Source: OECD, OPTIC Model.

Table B.6. Calculation of the level of public support for LPG buses

(MDL)

Year	0	1	2	3	4	5	6	7	8
Investment costs for a new bus	4.73 mln
Difference in price compared to a standard bus	3.69 mln
Required public support	1.883 mln
Annual fuel cost savings	254 000	254 000	254 000	254 000	254 000	254 000	254 000	254 000	254 000
NPV	0

Source: OECD, OPTIC model.

Table B.7. Assumptions for calculating the level of public support for modern diesel buses

	Fuel consumption	Fuel price	Annual distance	Fuel costs per year MDL
Diesel Euro VI bus	50 l/100 km	16.5 MDL/l	46 000 km	380 000
Standard diesel bus	45 l/100 km	16.5 MDL/l	46 000 km	342 000
Annual difference				-38 000

Source: OECD, OPTIC Model.

Table B.8. Calculation of the level of public support for modern diesel buses

(MDL)

Year	0	1	2	3	4	5	6	7	8
Investment costs for a new bus	4.52 mln
Difference in price compared to a standard bus	3.48 mln
Required public support	3.14 mln
Annual fuel cost savings	-47 000	-47 000	-47 000	-47 000	-47 000	-47 000	-47 000	-47 000	-47 000
NPV	0

Source: OECD, OPTIC Model.

The above calculations do not take into account possible reduced maintenance costs, as old buses tend to require more maintenance over time. On the other hand, the maintenance of modern technologies can be is more expensive, especially in terms of security concerns in using CNG or LPG, so it is assumed that bus replacement will be neutral in terms of maintenance costs.

The results of the calculation are presented in the "Subsidy" tab (Table B.10).

Table B.9. Subsidy calculation for public support for replacement of buses

	Costs per bus	Difference in price to standard bus	Annual distance	Annual fuel costs	Annual reference fuel costs*	Subsidy required per bus	Net cost to beneficiary per bus
	MDL mln	MDL mln	km	MDL mln	MDL mln	MDL mln	MDL mln
CNG	5.20	4.16	46 000	157 000	427 000	2.241	2.960
LPG	4.73	3.69	46 000	174 000	427 000	1.883	2.840
Diesel Euro VI	4.52	3.48	46 000	380 000	427 000	3.141	1.380

Note: *Reference fuel costs refer to old diesel buses.

Source: OECD, OPTIC Model.

Cost calculation

The cost calculation module under the tab "Costs" shows the estimated investment costs and the subsidy required by the CPT Programme. This information is provided in a table format that contains data on public transport in Moldova, the number of buses to be replaced, the type of new buses, total investment costs, the level of subsidy and the net costs to beneficiaries. In this module, users simply input factual information without making any decisions on the programme.

Table B.10. Investment costs, subsidies and net costs for beneficiaries

№	Type	City	Buses to be replaced			New buses						Need for CNG stat-ion	Investment costs
			Type			Bus			Mini-bus		Trolley bus		Bus			Mini-bus		CNG stat-ions	Trolley buses	Total
			Buses	mini-buses	Trolley buses	Diesel	CNG	LPG	Diesel	LPG	Elect-ricity		Diesel	CNG	LPG	Diesel	LPG
1	Urban	Chisinau	60	555	25	42	42	43	43	52	50	0	190	218	203	87	105	0	260	1 063
2	Urban	Balti	16	86	6	8	8	7	8	13	12	0	36	42	33	16	26	0	62	216
3	Suburban	Chisinau	173	337	0	71	71	70	71	71	0	0	321	369	331	143	143	0	0	1 307
4	Suburban	Balti	29	32	0	10	11	10	11	11	0	0	45	57	47	22	22	0	0	194
5	Inter-city	Chisinau	319	1 545	0	185	185	184	185	185	0	0	836	962	869	373	373	0	0	3 413
6	Inter-city	Balti	18	41	0	8	8	7	8	8	0	0	36	42	33	16	16	0	0	143
7	Inter-city	Other regions	279	1 361	0	324	0	162	163	163	0	0	1 464	0	765	329	329	0	0	2 887
Total			894	3 957	31	648	325	483	489	503	62	0	2 929	1 689	2 282	986	1 014	0	322	9 223

 

№	Type	City	Subsidy								Net costs for beneficiary
			Bus			Mini-bus		CNG stations	Trolley bus	Total	Bus			Mini-bus		CNG stations	Trolley buses	Total
			Diesel	CNG	LPG	Diesel	LPG				Diesel	CNG	LPG	Diesel	LPG
1	Urban	Chisinau	142	109	102	56	58	0	130	597	47	109	102	30	47	0	130	466
2	Urban	Balti	27	21	17	10	14	0	31	121	9	21	17	6	12	0	31	95
3	Suburban	Chisinau	241	185	165	93	79	0	0	762	80	185	165	50	64	0	0	545
4	Suburban	Balti	34	29	24	14	12	0	0	113	11	29	24	8	10	0	0	81
5	Inter-city	Chisinau	627	481	435	243	205	0	0	1 990	209	481	435	131	168	0	0	1 423
6	Inter-city	Balti	27	21	17	10	9	0	0	84	9	21	17	6	7	0	0	59
7	Inter-city	Other regions	1 098	0	383	214	181	0	0	1 875	366	0	383	115	148	0	0	1 012
Total			2 197	845	1 141	641	558	0	161	5 542	732	845	1 141	345	456	0	161	3 681

Source: OECD, OPTIC Model.

Emission reductions calculation

The emission reductions calculation module, under the tab "Emissions", shows the estimated annual emission reduction by type of pollutant. This information is provided in an Excel table (Table B.12) that contains data on transport sector in Moldova, the number of buses to be replaced, the type of new buses, the emissions from old buses, emissions from new buses, and emission reduction. In this module, users simply input the factual information without making decisions on the CPT Programme.

Table B.11. Emission reductions based on the purchase of new buses

№	Type	City	Buses to be replaced			New buses						Buses to be replaced
			Type			Bus			Mini-bus		Trolley-bus	Emissions
			Buses	Mini-buses	Trolley-buses	Diesel	CNG	LPG	Diesel	LPG	Electricity	CO2 (t)	CO (kg)	NOx (kg)	PM 2.5 (kg)	SO2 (kg)
1	Urban	Chisinau	60	555	25	42	42	43	43	52	50	26 371	41 609	182 464	3 752	3 496
2	Urban	Balti	16	86	6	8	8	7	8	13	12	5 004	7 851	34 427	708	660
3	Suburban	Chisinau	173	337	0	71	71	70	71	71	0	33 410	53 856	236 171	4 856	4 525
4	Suburban	Balti	29	32	0	10	11	10	11	11	0	4 805	7 746	33 968	698	651
5	Inter-city	Chisinau	319	1 545	0	185	185	184	185	185	0	91 593	147 645	647 462	13 312	12 405
6	Inter-city	Balti	18	41	0	8	8	7	8	8	0	3 669	5 914	25 935	533	497
7	Inter-city	Other regions	279	1 361	0	324	0	162	163	163	0	80 424	129 641	568 509	11 689	10 892
Total			894	3 957	31	648	325	483	489	503	62	245 277	394 262	1 728 936	35 548	33 124

 

№	Type	City	New buses (Emissions)					Emission reduction
			CO2 (t)	CO (kg)	NOx (kg)	PM 2.5 (kg)	SO2 (kg)	CO2 (t)	CO (kg)	NOx (kg)	PM 2.5 (kg)	SO2 (kg)
1	Urban	Chisinau	11 572	8 538	37 583	40	312	14 799	33 071	144 881	3 711	3 183
2	Urban	Balti	2 249	1 573	7 019	8	58	2 755	6 278	27 408	700	602
3	Suburban	Chisinau	17 062	13 551	61 234	66	498	16 349	40 305	174 937	4 790	4 027
4	Suburban	Balti	2 516	1 978	8 928	10	72	2 290	5 768	25 040	689	579
5	Inter-city	Chisinau	44 565	35 511	160 084	172	1 304	47 029	112 134	487 377	13 140	11 101
6	Inter-city	Balti	1 862	1 414	6 607	7	52	1 807	4 500	19 328	526	445
7	Inter-city	Other regions	40 552	31 061	159 153	122	1 366	39 872	98 580	409 355	11 567	9 526
Total			120 377	93 625	440 610	425	3 662	124 900	300 637	1 288 326	35 123	29 463

Source: OECD, OPTIC Model.

Programme costing and environmental effects

The CPT Programme costing and environmental effects module is under the tab “Decision”. This is the main module for supporting decision making. It can be used for the automatic calculation of the programme costs as well as for manual adjustments.

The upper part of the screen contains the information on the programme target. Users may define one of the following programme targets:

• investment costs

• subsidy budget (amount of funding available for subsidies)

• CO₂ emission reduction

• CO emission reduction

• NO_x emission reduction

• PM2.5 emission reduction

• SO₂ emission reduction.

By clicking on the “Go” button to the right of the respective target (Table B.13), the model calculates the programme financial envelope necessary to achieve the target, for that target only, excluding the other targets.

Table B.12. Adjusting programme costs and environmental effects

Source: OECD, OPTIC Model.

The algorithm for the programme cost calculation is as follows:

• The model reviews the information on public transport for each city, in the order provided in the table in the “Transport” tab. The review is done in three iterations, starting from the urban centres and then respectively for suburban and inter-city connections.

• First, the model determines whether the city has any potential for CNG buses; if so, the model proposes the replacement of an old bus by a CNG bus.

• Then, the previous step is repeated until the target is reached or all old buses in a given iteration are replaced.

• If the city does not have the potential for CNG buses, the model completes the same steps with Euro VI diesel buses.

• If the city lacks the potential for either CNG or Euro VI diesel buses, the model proceeds through the same steps with LPG buses.

• The costs of CNG stations are also taken into account. If the number of buses replaced is higher than 100, it is assumed that a CNG station is a commercial project and a subsidy is not required. Existing CNG stations in Bishkek and Osh are taken into account.

The results are presented in an Excel table (Table B.14) that contains basic information on the number of new buses, investment costs, subsidies and emission reductions per year. If users want to see details, the “Emissions” or “Costs” tabs should be used (described earlier).

Table B.13. Relationship between programme costs and environmental effects

№	Type	City	New buses						Investment costs	Subsidy	Emission reduction per year
			Bus			Mini-bus		Trolleybus
			Diesel	CNG	LPG	Diesel	LPG		million MDL	million MDL	CO2 (t)	CO (kg)	NOx (kg)	PM 2.5 (kg)	SO2 (kg)
1	Urban	Chisinau	42	42	43	43	52	50	1 063	597	14 799	33 071	144 881	3 711	3 183
2	Urban	Balti	8	8	7	8	13	12	216	121	2 755	6 278	27 408	700	602
3	Sub-urban	Chisinau	71	71	70	71	71	0	1 307	762	16 349	40 305	174 937	4 790	4 027
4	Sub-urban	Balti	10	11	10	11	11	0	194	113	2 290	5 768	25 040	689	579
5	Inter-city	Chisinau	185	185	184	185	185	0	3 413	1 990	47 029	112 134	487 377	13 140	11 101
6	Inter-city	Balti	8	8	7	8	8	0	143	84	1 807	4 500	19 328	526	445
7	Inter-city	Other regions	324	0	162	163	163	0	2 887	1 875	39 872	98 580	409 355	11 567	9 526
Total			648	325	483	489	503	62	9 223	5 542	124 900	300 637	1 288 326	35 123	29 463

Source: OECD, OPTIC Model.

Users may change the project pipelines by providing their own information on the number of new buses. Then the calculations are updated accordingly.

Programme costing for Phase 1 (pilot phase) and Phase 2 (scaling-up phase)

In the spreadsheet titled “Programme targets”, (Table B.15) users may define whether the calculation is being done for the pilot phase (Phase 1), which covers only two cities, or for Phase 1 and 2. The user may also define whether normative or real emission factors are used in the calculation. The third parameter defined by the user is the scenario for Phase 2, which may be as follows:

• Scenario 1: Replacement of oldest buses (those remaining after Phase 1) operating in urban/suburban areas of the pilot cities.

• Scenario 2: Replacement of the buses as in Scenario 1, as well as those operating inter-city connections (which covers urban/suburban transport in other cities).

Table B.14. Adjusting programme targets

Source: OECD, OPTIC Model.

By clicking on the “Go” button to the right of the defined scenario, the model calculates the programme costs and emission reductions. The targets are thus ignored.1

Sources of information used in the assumptions

The current version of the model uses information from different sources, both Moldovan and international. This section describes the sources of information for each assumption used:

• Data on urban public transport (number of buses, fuel type and age) were provided by the cities of Chisinau and Balti, the National Agency of Road Transport (ANTA), the Ministry of Transport and Roads Infrastructure (since September 2017, within the Ministry of Economy and Infrastructure), and the Ministry of Environment (since September 2017, part of the Ministry of Agriculture, Regional Development and Environment), as well as by private minibus operators in Chisinau and Balti.

• The average prices of buses were obtained from estimates from European Bank for Reconstruction and Development (EBRD) tenders, municipal tenders, statements of bus and minibus operators in questionnaires, and market research on the internet.

• The fuel prices were obtained from market research on the main distribution companies on the internet and in particular the national regulator ANRE.

• Fuel consumption was calculated by reviewing technical information of bus producers and several bus utilities introducing new buses (Der Betrieb mit Flüssiggas als Alternative zum Dieselantrieb/(Operating with LPG as an alternative to diesel propulsion);2 Cost and Benefits of Clean Technologies for Bus Rapid Transit (BRT): Summary of Results for Kampala (ICCT, 2012[6]); Comparison of Modern CNG, Diesel and Diesel Hybrid-Electric Transit Buses: Efficiency and Environmental Performance (MJB&A, 2013[7]); CNG vs. Diesel Bus Comparison; Infrastructure for Alternative Fuels (European Expert Group on Future Transport Fuels, 2011[8]) 3 and A Realistic View of CNG Vehicles in the US (Nath R. et al, 2014[9]).

Emission factors

The emission factors were taken from:

• The section on “Exhaust Emissions of European Monitoring and Evaluation Programme” in the European Environment Agency (EEA) Air Pollution Emission Inventory Guidebook 2013; Technical Guidance to Prepare National Emission Inventories (EEA, 2016[10]).

• Euro II-VI emission standards.

• Euro II-V fuel standards (for SO₂).

• The revised 1996 Intergovernmental Panel on Climate Change (IPCC) Guidelines for National Greenhouse Gas Inventories, Vol. 3: The Reference Manual (IPCC, 1996[11]).

• The Emissions Factors Toolkit (EFT) published by Defra and the Devolved Administrations (Defra and the Devolved Administrations, 2017[12]).

• For electricity, the CO₂ Emission factor & transmission and distribution loss factor provided in the U4E Country report: http://united4efficiency.org/wp-content/uploads/2017/05/MDA_U4E-Country-Assessment-Report.pdf.

The various emission standards used in the calculations are provided in Table B.16. They are practically entirely based on the European emission regulations for new heavy-duty diesel engines, commonly referred to as Euro I-VI.

Table B.15. EU emissions standards for heavy-duty diesel engines

(g/kWh)

 

Tier	Date	Test cycle	CO	HC	NOx	PM
Euro I	1992 < 85 kW	Economic Commission for Europe of the United Nations (ECE/UN) Regulation-49	4.5	1.1	8.0	0.612
	1992 > 85 kW		4.5	1.1	8.0	0.36
Euro II	October 1996		4.0	1.1	7.0	0.25
	October 1998		4.0	1.1	7.0	0.15
Euro III	October 1999 Enhanced Environmentally friendly Vehicles (EEVs) only	European Stationary Cycle (ESC) and European Load Response (ELR)	1.0	0.25	2.0	0.02
	October 2000	ESC & ELR	2.1	0.66	5.0	0.10 - 0.13
Euro IV	October 2005		1.5	0.46	3.5	0.02
Euro V	October 2008		1.5	0.46	2.0	0.02
Euro VI	31 December 2013		1.5	0.13	0.4	0.01

Source: (EC, 2017[13]), Transport Emissions: Air Pollutant from Road Transport, http://ec.Europa.eu/environment/air/transport/road.htm (accessed 16 February 2017).

Similarly, the EU fuel standards for sulphur content for Euro 2-5, used in the calculations, are provided in Table B.16.

Table B.16. EU fuel standards for sulphur content

Name	EU Directive	European Committee for Standardization (CEN) Standard	Implementation date	Sulphur limit (ppm)
n/a	-	EN 590:1993 (d) EN 228:1993 (g)	October 1994	2 000
Euro 2	93/12/EEC	-	October 1996	500 (diesel)
Euro 3	93/12/EEC	EN 590:1999 (d) EN 228:1999 (g)	January 2000	350 (diesel); 150 (petrol)
Euro 4	98/70/EC	EN 590:2004 (d) EN 228:2004 (g)	January 2005	50*
Euro 5	2003/17/EC	EN 590:2009	January 2009	10, 10**

Note: * “Sulphur-free” 10ppm fuel must be available; ** non-road fuels limit

Source: (EC, 2017[13]), Transport Emissions: Air Pollutant from Road Transport, http://ec.Europa.eu/environment/air/transport/road.htm (accessed 16 February 2017).

On the other hand, the estimated CO₂ emission factors for a number of pollutants emitted by European heavy-duty diesel vehicles come from the Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories and its Reference Manual (IPCC, 1996[11]) (Table B.18).

Table B.17. Estimated CO₂ emission factors for European heavy-duty diesel vehicles

	CO2
Total g/km	770
g/kg fuel	3 140
g/MJ	74

Source: (IPCC, 1996[11]), Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories, Volume 3: The Reference Manual, Intergovernmental Panel on Climate Change, Mexico City, www.ipcc-nggip.iges.or.jp/public/gl/invs6.html.

The current norms for air pollution and CO₂ emissions can be taken from the EMEP/EEA Air Pollution Emission Inventory Guidebook 2016 (EEA, 2016[10]). Table B.19 presents the Tier 1 approach to measuring exhaust emissions (explained in the source document for the table).

Table B.18. Tier 1 air pollution emission of heavy-duty diesel vehicles

(g/kg fuel)

	CO	NMVOC	NOx	PM	N2O
Diesel	7.58	1.92	33.37	0.94	0.051
CNG (buses)	5.70	0.26	13.00	0.02	n.a.

Source: (EEA, 2016[14]), EMEP/EEA Air Pollution Emission Inventory Guidebook 2016. Technical Guidance to Prepare National Emission Inventories. Part B: Sectoral Guidance Chapters – Road Transport 2018, www.eea.europa.eu/publications/emep-eea-guidebook-2016/part-b-sectoral-guidance-chapters/1-energy/1-a-combustion/1-a-3-b-i/view.

The EME/EEA Air Pollution Emission Inventory Guidebook 2016 is also used as a source for estimating the CO₂ emission factors for different fuels used in operating heavy-duty vehicles (Table B.20).

Table B.20. Tier 1 CO₂ emission factors for different road transport fossil fuels, all vehicle types

Fuel type	gCO2 / kg of fuel*
Petrol	3 169
Diesel	3 169
LPG**	3 024
CNG (or LNG)***	2 743

Note: *CO₂ emission factors are based on an assumed 100% oxidation of the fuel carbon (ultimate CO₂); ** LPG assumed to be 50% propane + 50% butane; *** CNG and LNG assumed to be 100% methane.

Source: (EEA, 2016[14]), EMEP/EEA Air Pollution Emission Inventory Guidebook 2016. Technical Guidance to Prepare National Emission Inventories. Part B: Sectoral Guidance Chapters – Road Transport 2018, www.eea.europa.eu/publications/emep-eea-guidebook-2016/part-b-sectoral-guidance-chapters/1-energy/1-a-combustion/1-a-3-b-i/view.

A couple of sources were used for fuel consumption values used in the model, combined with the authors’ own assumptions, particularly for LPG consumption volumes (Table B.21).

Table B.19. Assumed fuel energy content and consumption of heavy-duty vehicles

Fuel type	Energy (unit)	Consumption (g/km)
Petrol	8.77 (kWh/l)	300*
Diesel	9.86 (kWh/l)	240
CNG	13.16 (kWh/kg)	500
LPG	6.6 (kWh/l)	340*

Note: * Own assumptions.

Source: (EEA, 2016[14]), EMEP/EEA Air Pollution Emission Inventory Guidebook 2016. Technical Guidance to Prepare National Emission Inventories. Part B: Sectoral Guidance Chapters – Road Transport 2018, www.eea.europa.eu/publications/emep-eea-guidebook-2016/part-b-sectoral-guidance-chapters/1-energy/1-a-combustion/1-a-3-b-i/view; www.erdgasautos.at (in German, accessed 14 March 2019).

It was assumed that the emission factors for old engines are the same as for a new one. However, in new engines energy efficiency is higher and fuel consumption 10% lower than in buses more than 5 years old, 15% lower than buses of more than 10 years old, and 25% lower than buses of more than 15 years old.

The specific emission factors used in the model are provided in Table B.2 above. The emission factors presented in Table B.2, however, are based on maximum levels, according to specific norms. The real emissions may vary, mainly because normative emissions are tested in laboratory conditions and not in actual traffic. This is a concern primarily in the case of diesel engines, where emission reduction depends on the installed emission reduction equipment. In the case of CNG and LPG, emissions are less problematic, because lower emissions are mainly the result of using cleaner fuels.

In 2014, the ICCT issued a report on real-world exhaust emissions from modern diesel cars presenting measurements of real emissions. The analysis showed that real-world emissions of CO₂ and NO_x are higher than the limits (respective Euro norms) – by an average of 40% and 70%, respectively (Franco et al., 2014[15]).

Figure B.1. Percentage of tested vehicles that exceed Euro limits in urban cycle

Note: The “window” represents a sample.

Source: (Franco et al., 2014[15]).

Thus, the model also offers an alternative set of emission factors taking into account the fact that real emissions may exceed normative ones. Table B.21. presents the real emission factors used in the model.

Table B.20. Assumed emissions factors adjusted to real values (per km)

Engine and fuel type	CO2 (kg/km)	CO (g/km)	NOx (g/km)	PM2.5 (g/km)	SO2 (g/km)
Diesel Euro II	1.5137	2.4400	10.7000	0.2200	0.2050
Diesel Euro II>5 y.	1.6650	2.6840	11.7700	0.2420	0.2255
Diesel Euro II>10 y.	1.8164	2.9280	12.8400	0.2640	0.2460
Diesel Euro II>15 y.	1.9678	3.1720	13.9100	0.2860	0.2665
Diesel Euro VI	1.0685	0.2230	4.2387	0.0023	0.0205
CNG (EEV standard)	0.9350	0.2400	2.5000	0.0050	0.0000
LPG	1.0258	1.9200	5.0000	0.0050	0.0652

Source: OECD, OPTIC Model.

The user can change both normative and real emission factors according to modelling needs.

Notes

← 1. The model assumes that an average bus operates 330 days per year.

← 2. For information on CNG vehicles, see www.erdgasautos.at (in German).

← 3. See www.bus.man.eu/cng_optimizer/index.html (accessed 25 February 2017).